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Worker "fishing" for niicrohes through a microscope from a colony
growth on transparent nutrient-jelly in glass Petri dish

WHO'S WHO
AMONG THE MICROBES

BY
WILLIAM H. PARK, M.D.

AND

ANNA W. WILLIAMS, M.D.

*»»fe;V«;«*»

TLLTTSTRATED

THE CENTURY CO.

NEW YORK LONDON

First printing

Printed in U. S. A.

T. MITCHELL PRUDDEN

PREFACE

The follo\\ang sketches grew out of a series of radio
talks on communicable diseases and their microbes. The
increasing demand for information suggested that peo-
ple were deeply interested in these invisible, omnipresent
enemies and friends. The thought occurred to The Cen-
tury Co. that the information given in these talks might
be more useful in a permanent shape. We were consulted
with the result that the subject matter was elaborated
to form this small volume.

The question of the relationship of microbes to man's
welfare is so vitally important and many sided that any
effort made to show some of its sides seems worth while.

We have endeavored to described simply and ac-
curately the most important facts known that help us
determine how and why some microbes are harmful to
man, others harmless and still others helpful. We also
tell how man can use available knowledge to protect
himself against harmful ones and utilize more fully the
activities of the useful.

We wish to express our great appreciation of the
kindly aid of Anna I. and Harriet von Sholly in reading
the manuscript and of Amelia R. Wilson in its pre-
liminary critical typing.

The Authors.

CONTENTS

PAGE

CHAPTES

I. Early Discoveries 3

Menace of the unknown — Invisible forces — >
Fighting in the dark — Glimmerings of dawn
— Revelations of first lenses — Whence? —
How?— WTiy?

II. How Microbes Become Better Known . . 17
Through the microscope — By use of stains — '
By the use of culture media.

III. How Microbes Live and Act 36

How they behave under different conditions
— Helpful, harmless, harmful activities —
How they are carried to individuals and from
one individual to another.

IV. How Nature Reacts to Microbes ... 51

Limitations of nature's methods — Man's as-
sistance— Natural and acquired immimity to
poisonous microbes.

V. Family Relationships of Microbes ... 69

As determined by humans who know little
about them, hence their constant regrouping
— "Family tree."

VI. The Coccus Family (Coccacece) .... 84

Pus producers — Blood invaders — Lung at-
tackers— Brain membrane inflamers — Cheese
makers.

VII. Nitrogen-Using Family (Nitrobacteriacece) . 101

Soil microbes — Life-giving forms in the life
cycle of plants and animals — Oxidizers of
simple chemical combinations,
vii

'iii CONTENTS

CHAPTER PAGB

VIII. Microbes Living in the Intestines . . . 110

The "long life" microbe — The signal bacillus
— The food-poisoning group — The typhoid
dysentery group.

IX. Pasteur's Tribe {Pasteur elleae') . . . . 131

The "black death" bacillus — The ground
squirrel or rabbit disease bacillus.

X. Blood-Thirsty Tribe {Hemophlilece) . . . 141

The intriguing influenza bacillus — The ex-
citing whooping-cough bacillus.

XI. The Resistant Family (Bacillacece) . . . 150

Spore-bearers in the soil — Forms resisting
canning — The anthrax bacilli — The lock-jaw
bacillus — War wound bacilli.

XII. The Club-Shaped Group (Part of the family

Mycobacteriacece) 164

The diphtheria bacillus clan and relatives.

XIII. The Group of the Acid-Fast Bacilli (Myco-

bacterium) 178

Bacilli causing tuberculosis and the "unclean
disease/' leprosy — The glanders bacillus.

XIV. The Comma Family and Cholera (Spiril-

lacece) 190

XV. The Coiled-Hair Family (Spirochcetecece) . 204

The "pale" spirochete and the immoral dis-
ease— Spirochetes in relapsing fever and in
yellow fever.

XVI. The Branching Family (Actinomycetacece) . 219

The lumpy-jaw microbe — Infrequent but in-
sidious attackers of human beings — Decom-
posers of organic matter.

CONTENTS

CHAPTER

XVII.

XVIII.

Yeasts and Molds

Alcohol producers — Bread raisers — Cheese
flavorers and ripeners — Decomposers of or-
ganic matter — Infrequent producers of dis-
ease.

Animal Microbes or Protozoa ....

The amoeba as a fighter — The misnomer ma-
laria— 'Protozoa in mosquitos and man, in
ticks and Texas fever — Sleeping sickness
and the boring animal — The animal causing
dum-dum disease.

XIX. Unknown Microbes. Filterable Viruses

Ultra microbes, the smallest of all, the cause
of yellow fever, rabies, smallpox and a num-
ber of other diseases.

XX. Man Making Use of His Acquaintance with
Microbes to Protect Himself. A Summary

Clean milk — Clean water — Clean foods in
general — Protection against disease germs
and carriers.

PAGE

229

239

252

272

Index 297

ILLUSTRATIONS

WORKER FISHING FOR MICROBES THROUGH A MICRO-
SCOPE FROM A COLONY GROWTH ON TRANSPARENT

NUTRIENT-JELLY IN GLASS PETRI DISH . . Frontispiece

FACING PAQB

DIFFERENT TYPES OF COLONIES OF MICROBES FROM SUB-
WAY AIR GROWN ON TRANSPARENT AGAR JELLY FOR
24 HOURS AT 36° C. NATURAL SIZE 20

WORKER READY TO FISH FROM COLONIES OF MICROBES

WITHOUT THE AID OF THE MICROSCOPE .... 21

WORKER USING FERMENTATION TUBE CONTAINING SUGAR
BROTH FOR GROWING MICROBES, TO SHOW THEIR
POWERS TO PRODUCE ACID AND GAS AND GROW WITH-
OUT AIR 28

CORNER OF MEDIA ROOM SHOWING WORKERS PREPARING
GLASSWARE TO BE STERILIZED IN HOT AIR STERILIZER,
AT RIGHT 28

SOME TYPES OF THE THREE GREAT CLASSES OF MICROBES 29

CERTAIN PARTS OF BACTERIA 82

ANTHRAX BACILLI GROWING IN SPLEEN OF MOUSE AND

SHOWING A CAPSULE 33

COCCI GROWING IN CHAINS 80

STREPTOCOCCI DISSOLVING RED BLOOD CELLS .... 80

COCCI GROWING IN BUNCHES LIKE GRAPES 81

COCCI GROWING IN PAIRS WITHIN PUS CELLS, THE GONO-

COCCUS MAKING A VERY DISTINCTIVE APPEARANCE . 81

INJECTING PNEUMONIA SPUTUM INTO THE BELLY OF A
WHITE MOUSE TO HELP DETERMINE TYPE OF PNEU-
MOCOCCUS 96

DRAWING BLOOD FROM HORSE THAT CONTAINS PNEUMO-

COCCUS ANTIBODIES 96

xii ILLUSTRATIONS

FACINO PAGE
STEPS IN THE PROCESS OF CONCENTRATING AND REFINING

ANTITOXIN 97

HUNTING FOR TYPHOID CARRIERS, LOOKING FOR COLONIES
OF TYPHOID BACILLI IN GROWTHS OF DILUTIONS,
MADE FROM FECES OF CASE UNDER INSPECTION . . 128

A. STAINED TYPHOID BACILLI FROM 24-HOUR AGAR CUL-
TURE MAGNIFIED 1 000 DIAMETERS. B. TYPHOID BACILLI
STAINED TO SHOW FLAGELLA 129

MAKING TYPHOID VACCINE 129

HUNTING FOR PLAGUE FLEAS ON RATS, IN NEW YORK CITY

PORT 144

NEW YORK HEALTH DEPARTMENT WORKER AIDING FED-
ERAL HEALTH SERVICE IN ITS HUNT FOR PLAGUE-
INFECTED RATS 144

THE TWO BEST KNOWN MEMBERS OF THE BLOOD-THIRSTY

TRIBE HEMOPHILE^ 145

MICROBES IN TISSUES OF TEST ANIMALS 152

SOME CHARACTERISTICS OF CERTAIN IMPORTANT MICROBES 153

TECHNIC OF MAKING CULTURE FROM DIPHTHERIA THROAT 160

DIPHTHERIA BACILLI SHOWING LARGE CLUB-SHAPED FORMS 161

COMPARATIVE COLONY GROWTHS FROM CLEAN AND DIRTY

MILK 161

RESULTS FROM INJECTING DIPHTHERIA TOXIN INTRA-

DERMALLY 176

DR. SCHICK MAKING THE SCHICK TEST THE INTRADERMAL

TEST WITH DIPHTHERIA TOXIN ON A GROUP OF SCHOOL
CHILDREN 176

THE $175,000 HORSE, ONE OF OUR MOST FAMOUS "ANTI-
TOXIN HORSES," CALLED "oLD FAITHFUL" BECAUSE HE
PRODUCED SUCH HIGH GRADE ANTITOXIN FOR SO LONG
A TIME 177

MAKING THE CALMETTE VACCINE THAT IS BEING TRIED

FOR ITS PROTECTIVE WORTH AGAINST TUBERCULOSIS 192

PROTECTING AN INFANT FROM TUBERCULOSIS . . . . 193

ILLUSTRATIONS xiii

FACING PAGE

THE RELAPSING FEVER SPIROCHETE-BORRELLA RECURRENTIS

IN BLOOD OF PATIENT 208

THE "pale SPIROCHETa" OF SYPHILIS TREPONEMA PAL-
LIDUM 208

A CORNER OF THE NEW YORK CITY HEALTH DEPARTMENT

WASSERMANN LABORATORY 209

STAGES IN THE LIFE OF DIFFERENT TYPES OF THE MA-
LARIAL PROTOZOA GROWING ON AND IN RED BLOOD
CELLS 240

PROTOZOA CALLED LEISHMAN-DONOVAN BODIES THAT WERE
THOUGHT TO BE SPOROZOA UNTIL THEY WERE GROWN
IN PURE CULTURES WHEN THEY DEVELOPED FLAGEL-
LATED FORMS LIKE THOSE IN THE ILLUSTRATION,
WHICH PLACED THEM AMONG THE FLAGELLATES . 241

PREPARATION OF BOVINE VACCINE FOR USE AGAINST

SMALLPOX 256

SEALING TUBES OF BOVINE VACCINE, FOR USE AGAINST

SMALLPOX 257

COUNTING COLONIES GROWN FROM DILUTIONS OF SAMPLES

OF THE city's MILK SUPPLY 280

CORNER OF LABORATORY FOR BACTERIOLOGICAL EXAMINA-
TION OF MILK 280

ONE OF THE COMMITTEE OF FAMOUS PUBLIC HEALTH OF-
FICERS WHO THEMSELVES CARRIED THROUGH EXTEN-
SIVE EXPERIMENTS TO TEST THE PRACTICAL EFFICACY
OF PASTEURIZATION UPON THE POISONOUS MICROBES
THAT MIGHT FIND THEIR WAY INTO UNPROTECTED
MILK 281

FIGURES

FIGURE PAGE

1 HOLLOW SLIDE WITH COVER-GLASS 19

2 COMPARATOR BLOCK 24

3 DIAGRAM OF INNER CONSTRUCTION OF HORIZONTAL

AUTOCLAVE 25

4 ARNOLD STEAM STERILIZER 26

5 COMPARATIVE SIZE OF BACTERIA 32

6 BUCHNER's ANAEROBIC TUBE 39

7 MICROSCOPIC FIELD 61

8 MICROSCOPIC FIELD 62

9 HYPOTHETIC TREE OF EVOLUTION OF MICROBES . . 80

10 CHIEF COMPARATIVE CHARACTERISTICS OF CULEX AND

ANOPHELES 245

WHO'S WHO
AMONG THE MICROBES

CHAPTER I
EARLY DISCOVERIES

Menace of the unknown — Invisible forces — Fighting in the

dark — Glimmerings of light — Revelations of the

first lenses — Whence ? — How ? — Why ?

The world of microbes, that world of minutest living
beings, had existed, in^'isible and unknown to man,
throughout the ages. Only comparatively recently have
its ever-present myriads been forced upon our atten-
tion. As late as the middle of the nineteenth century
disease and death brought about by germs remained a
mystery — due, believed the many, to malignant spirits.
Only with the development of the microscope was it
possible for man to be certain of the presence of such
tiny creatures and to begin intelligently his battle to
study and control them.

It is true that even as early as 40 b.c. an occasional
real thinker surmised that minute organisms which
the eye cannot see enter the body and cause disease.^
And a few investigators of pre-microscope days went
so far as to say that certain diseases were probably
caused by a contagmm-vivium — a li\ang virus or
poison. But the majority of people in those days stiU
thought that the mystery of disease must be referred to
gods or devils either directly or through magic or

* Osier, "The Evolution of Modern Medicine." New Haven: Yale
University Press, 1923.

4 WHO S WHO AMONG THE MICROBES

witchery. And to what lengths their obsession led them
for many years we all know not only from the customs
of ignorant savages but from the tragic history of
more intelligent people. Witchcraft in Salem and else-
where may be recalled as one of the many horrible situ-
ations resulting from the ignorance of fanatics.

This behef that disease was due to some malign in-
fluence that used an agency often belonging to the in-
visible world was true in a sense other than these be-
wildered people realized. The idea that disease was
sometimes sent as a punishment or corrective by the
gods went along with other early crude imaginings.
Little wonder that people prayed and made sacrifices
to their gods to avert the pestilences that descended
upon them and the dread diseases that stayed with
them they knew not why except it might be for their
sins known or unknown. And the conviction that the
gods in their wise providence sent or allowed these
terrors as punishment became firmly established. Men
exercised their ingenuity in devising ways of propi-
tiating the angry gods. In very early times feasts and
dances were given to appease divine wrath. Later, fasts
with sackcloth and ashes were resorted to in endeavors
to obtain the favor of the offended deity.

In this day of our knowledge of the prevention of
infectious diseases we can scarcely realize the state of
mind of people who constantly faced the menace of the
unknown in the fear of being attacked by such terrible
epidemic scourges as the black death (bubonic plague),
yellow fever, cholera, smallpox, and the endemic or
ever-present diseases of tuberculosis, sypliilis and ma-
laria, without knowing anything about their cause,
prevention and cure. And in addition they saw their

EARLY DISCOVERIES 5

crops destroyed by blights and their flocks swept away
by still other mysterious diseases.

Defoe's famous "Plague Year" (1665) gives a mi-
nute vivid picture of the fearful ravages from plague in
those times and of the horrible way the authorities, in
their ignorance, handled the victims. One in every six
or seven persons died, and the dead, and sometimes the
dying, were thrown together into large pits. It is true
they were covered with quicklime, which is a good
germicide. Now with our knowledge of the nature of
plague and its spread we have demonstrated one of
the most clear-cut relationships between cause and pre-
vention, and have shown the satisfactory results of pre-
ventive treatment based upon this knowledge in the
areas where it is possible to carry out these measures.
Thus in the United States there is now only an occa-
sional sporadic case started by infection brought in
from outside, though earher a small epidemic of plague
developed even here before we had learned how com-
paratively easy it is to prevent its spread.

Copeman ^ dramatically describes the early history
of the terrors from smallpox, perhaps the most dreaded
of all the formerly uncontrolled scourges, because it
had become endemic, always present. Not only did it
frequently cause death, but, what might be worse, it
often destroyed the beauty, the physical personality
even, of the survivors, "turning the babe into a change-
Hng at which the mother shuddered, and making the
eyes and cheeks of the betrothed maiden objects of
horror to the lover." ®

' S. Moncton Copeman, "Vaccination." London : Macmillan & Co.,
1899.
*Macaulay's "History of England." Account of the year 1694,

6 WHO S WHO AMONG THE MICROBES

These shocking conditions were due chiefly to the
fact that people knew nothing about the activities of
these microscopic or ultra-microscopic organisms in
disease and health.

The truth only commenced to be discovered, and then
slowly, when the microscope began to reveal its won-
ders. Even when the stupendous discovery was made
that minute forms of life too small to be seen with the
naked eye were swarming in myriads throughout na-
ture, in air, water, soil, observers did not at first connect
these tiny creatures with the cause of definite diseases.
For they were primarily found by van Leeuwenhoek,
the first of de Kruif's magnetic microbe hunters, in
quite harmless vehicles, such as rain-water, the top
layers of the soil and in healthy human excretions.

When these minute germs were first seen s^vimming
around in fluids as fish do, their discoverers thought
that they had found some new little animals — animal-
cules; so they searched for their heads, eyes, tails and
other parts similar to those belonging to the larger
known animals. When they could not find these struc-
tures, the hunters thought it was due to the fact that
their lenses did not magnify enough, and many were
the attempts to make better lenses.

Now we know that the majority of the forms they
first saw were the very simplest of living creatures,
for the most part with no clearly discernible structure ;
that is, they were motile bacteria belonging to the veg-
etable kingdom. Only a small number were animals,
and even these were single-celled with simply a few
differentiated parts called organelles.

While it was exciting enough to watch through the
lenses these little creatures girate around with all sorts

EARLY DISCOVERIES 7

of fantastic motions, the thoughts as to what they might
mean, where they came from, how they live were far
more alluring to the few who knew about this great
discovery and busied themselves with attempts to find
out all about these mysterious forms of Hfe.

First the searchers asked themselves, "Where did
these minute living forms come from ?" "How were they
created?" The majority thought that the answer to
these questions was that these creatures were continu-
ally being generated spontaneously under certain con-
ditions of heat, moisture and food; and many were
the grotesque ideas these observers had of just how
this generation took place.

The few most thoughtful investigators believed that
these lowly organisms gi'ew from preexisting Hke or-
ganisms and that their beginnings lay, as did that of
the beginning of aU Hfe, in the dim unknown past, or
that they were created "in the beginning b}' God."

The many who beHeved that aU germs continued
spontaneously to generate were superficial observers,
who thought in ruts. The occasional ones like Redi
(1688) or Spallanzani (1769), who beheved the oppo-
site, were not only close observers but showed that they
were right by actually doing the things they claimed
could be done, in such a logical way and so fully con-
trolled against error that nearly everybody with at
least average intelhgence who became acquainted with
their work, even some of the most doubtful, were finally
conA'inced that under known conditions germs did not
spontaneously generate. The story of their convincing
demonstrations has often been told, but it cannot be too
often repeated, because it is such a good illustration of
wrong deductions from insufficient checks or controls

8 WHO S WHO AMONG THE MICROBES

against error, and right conclusions from sufficient
evidence properly controlled.

The sponsors of spontaneous generation said that if
one boiled broth made from vegetable or animal matters
the germs that might be present would certainly be
killed, and yet if such broth was kept from the air by
corking the bottles containing it, in a few days it would
be swarming with germs. Spallanzani decided that these
broths had not been cooked long enough to kill the most
resistant germs or that it had not been properly corked.
So he made a large quantity of broth and put some into
each of many glass flasks. Then after closing some of
the flasks by fusing with heat, and others by corking
with imperfectly fitted porous corks, he kept some in
boihng water for a few minutes and others for at least
one hour. After removing the flasks from the water he
kept them under observation for some time. At length
he saw that in all flasks that had been in boiling water
for only a short time the broth had become turbid, due
to the growth of germs, and that of those that had been
in the boihng water for about an hour the fused flasks
remained free from germs, while a number of the im-
perfectly corked ones showed them.

His opponents answered him by claiming that the
boiling for so long a time without access to any air had
destroyed the power of the broth to generate germs
spontaneously.

Spallanzani soon showed that this was not true by
the simple process of exposing some of the boiled broth
in the fused flasks to the air, when the broth soon be-
came filled with growing germs. He said that germs
must produce seeds that are very resistant to heat. He
thus concluded before they were seen that these tiny

EAELY DISCOYEEIES 9

creatures could develop still more minute parts like
seeds which would contain the germ of the individual.
Pasteur, much later, showed that the reason why some
fluids required so much boiHng was because of the
presence of these very resistant seeds or spores which
had just been demonstrated by Perty (1852).

Pasteur's clear-cut experiments showed that no life
occurred in any fluids, however rich the mixture, if
such fluids were boiled sufficientl}^ and kept protected
from unfiltered air or other source of contamination.
These investigations of his, his telling demonstrations
and the heated arguments of his opponents lasted over
four j'ears. They are "vavidly told in Vallery-Radot's *
interesting "Life of Pasteur."

Finalh", after more than a century of controversy,
nearly every one agreed that these minute creatures
did not suddenly come into Hfe under an}^ of the con-
ditions observed.

One of the early practical results of this study on
spontaneous generation — one of far-reaching impor-
tance— was the introduction by Appert in 1804* of the
preser\'ing of foods by sterihzing them in cans.

With tliis greatly contested point of spontaneous
generation apparently settled, there was more time to
study other questions concerning these little creatures ;
but with all their endeavors, students did not get very
far in learning how the germs lived and what they
mean, because nobody had j'et learned how to separate
them easily one from the other so that each kind might
be groMTi b}^ itself in pure cultures. That came much
later. In the meantime, Ehrenberg (1838) and others

* Translated by Mrs. R. L. Devonshire. New York: McClure, Phillips
& Co., 1902.

10 WHO S WHO AMONG THE MICROBES

gave rough classifications of these minute forms based
upon physical appearance or morphology alone.

During all this time there slowly multiplied the num-
ber of observers who claimed that some of these germs
were probably the cause of certain diseases, and, as
usual, one or two were far ahead of others in their
powers to observe and deduce. First came Boyle just
about the time of Kircher's and Leeuwenhoek's dis-
coveries of germs (1659-1675), who said that infec-
tious diseases were probably due to fermentation caused
by animalcules. Then Lancisi (1718) inferred that
malaria was due to an animalcule. In 1753 Linnaeus
emphatically stated that all disease was due to fermen-
tation and putrefaction from an unknown living cause
which he called chaos. And Plenciz (1762), a Viennese
physician, published a more clear-cut statement. He
maintained that all infectious diseases must be caused
by micro-organisms, and each disease probably has its
own kind of germ. He gave as his reasons for this belief
the mode of infection, the unhmited development among
large numbers of individuals with the gradual spread
over wade areas, the incubation, course and resulting
immunity.

It had already been shown by the Chinese and the
Hindus that the inoculation of a susceptible person
with smallpox virus taken from a person suffering from
smallpox (which method was introduced into England
by Lady Montague in 1721) usually reproduced the
disease in a light form and caused immunity. Then in
1796 Jenner made his world-famous demonstrations
with cowpox virus. He was led to make his first trials
of it because of the oft-reiterated opinion of dairy

EAKLY DISCOVERIES 11

people that milkmaids, after developing cowpox con-
tracted while milking, did not get smallpox after ex-
posure to it. He showed that when inoculated into the
skin of human beings, this cowpox virus produced a
localized pustule resembling those of smallpox, but not
spreading, and that, marvelous to relate, after this
healed, the individual was subsequently protected from
infection with smallpox virus. Thus he proved that the
dairy people had been right in their observation.

That was indeed a wonderful discovery. Of course,
there were detractors and still are. That some parts of
the world are free from smallpox to-day because of
wide-spread and thorough vaccinations these detractors
will not accept. They claim there would be no smallpox
if there were no vaccination. They have only to watch
reports of outbreaks of smallpox and study the cases
minutely to become con^anced of the efficacy of thor-
ough vaccination. These carpers should learn, since
they apparently don't know, that each individual re-
sponds to vaccination in a different degree, so that in
some the immunity lasts only one year, in others longer
and in many for life; while there are even a very few
that do not make immune antibodies, so there are ex-
ceptional cases that appear to receive no benefit from
vaccination.

The next virus that was shown to produce a distinct
disease was the rabies virus (1813). The saHva of rabid
animals was shown to have the power of producing
rabies when inoculated into well animals. It had been
observed much earlier that man became "mad" after
the bite of a rabid animal. Much later, Pasteur did his
monumental work on the nature of the rabies virus and

12 WHO S WHO AMONG THE MICROBES

showed that a vaccine could be made that would keep
the vast majority of those bitten from developing
rabies.

Up to the middle of the last century certain medical
people continued to assert that the living nature of
contagion was too absurd an idea to waste time in re-
futing, but enthusiasts on the other side studied more
than ever to find evidence pointing to the truth of the
idea that germs are the cause of infectious diseases.

Henle in 1840 enunciated practically all of the
points quoted later as Koch's postulates. He said that
if a given germ causes a given disease, it should always
be found in that disease and in no other, and the tissues
containing it should produce the disease when inocu-
lated into other animals. When, finally, Pollender in
1849 actually demonstrated bacterial rods in the blood
of animals dying of anthrax, and Davaine (1850)
proved that only blood that contained these rods pro-
duced the disease when inoculated into healthy sheep,
many investigators were ready to go to the limit in
believing that all diseases are caused by germs and
that all germs are dangerous.

Later discoveries proved, of course, that such was
an extreme view. It is interesting to note as we scan
the history of medicine the fluctuating curve of empha-
sis placed by different writers upon the importance of
microbes to man. First germs were ignored or con-
sidered merely a curiosity. We still have ignorers. Then
when dangerous germs were demonstrated, all germs
were damned; some have been praised and others
damned irregularly since then.

Even to-day two popular books illustrate the fact
that we still have with us those who emphasize the

EARLY DISCOYEEIES IS

extremes of both sides. In one, entitled "The Conquest
of Disease," ^ the statement is emphatically made that
all germs are harmful to humans. On the other hand,
the book "Civihzation and the IVIicrobe" ^ states very
clearly and convincingly that the great majority of
these minute forms are extremely useful directly or in-
directly to civihzed man. Many instances are given of
their direct as well as indirect use to man. To beheve
that all are dangerous is the depth of pessimism; on
the other hand, to believe that all may become useful
or rendered innocuous within an appreciable time is
the height of optimism. Both appear to be unwarranted
by the known facts.

Not'VN-ithstanding their dread importance as disease
producers and their helpful importance in breaking
do\^Ti complex dead materials into simple compounds
for plant use and so enable Ufe to continue, microbes
are still ignored by the majority of people. Many
people don't want to be bothered with the thought of
all of the difficult problems concerning the relationship
of these minute forms to our welfare. But to those
people in whom the quality of curiosity, of wondering
over the mysteries of our beginnings and our endings,
is well developed, the fact that we know so Httle about
germs is all the more reason for being interested in
learning more about them. And when these eager
searchers think of the many minute forms that may
still be undiscovered because there is no way yet known
to demonstrate them, and that while some of these
germs may be harmful, some may be useful, and some

'David Masters, "The Conquest of Disease." New York: Dodd,
Mead & Co., 1925.

'Arthur I. Kendall, "Civilization and the Microbe." Houghton,
Mifliin Company, 1923.

14 WHO S WHO AMONG THE MICROBES

of the many harmless ones may be made useful, then
is their eagerness to learn about all these forms greatly
enhanced.

Fortunately for our welfare, there have always been
a few enthusiasts who have continued to study these
elusive protista, or first forms of life, and so we have
gradually come to know many of their characteristics.

An important characteristic to which we have al-
ready alluded is the formation of resistant spores or
seeds by some varieties. Perty, in 1852, was the first to
observe them. Others also saw them. Then Pasteur, as
we have said, showed that the presence of spores ex-
plained why we still have a growi;h of germs after they
have been submitted to a boiling temperature for a
short time.

A big discovery made by Perkins (1856) helped ma-
terially in the study of these forms. Perkins discovered
accidentally the value of aniline in dyes. This led to
the briUiant work of Weigert (1871) and of Ehrhch
(1887) on the use of these dyes in staining micro-
organisms, and later still to the work of Churchill and
others in the use of the dyes in differential cultural
methods and in treatment of certain infectious
diseases.

Then the discovery of how to get pure cultures of
these germs was of inestimable importance In studying
them. The first method de\dsed by Lister (1858), Pas-
teur and others was a dilution method. This method
required great patience and an almost innumerable
number of dilutions in order to catch a single organ-
ism. It is still used to obtain pure cultures of certain
protozoa, but it is now seldom employed for that pur-
pose in studying bacteria. In 1871 Klebs used hen's

EARLY DISCOVERIES 15

eggs as a culture medium. At the same time Koch
developed a jelly medium in which he obtained isolated
colony growth. Then came Hesse (1881) with her
agar-agar medium, which Koch later substituted so
successfully for the gelatine medium.

Just at this time, when it was demonstrated that the
suppuration of wounds was due to bacteria, the great
Enghsh surgeon Lister, incited by Pasteur's work,
introduced the use of antiseptics in his surgical opera-
tions. His work was epoch-making in its saving of Hfe.
Thus was stopped the formation of pus, even laudable
pus (really praiseworthy pus it was considered then),
as the small amount was called that was wrongly
thought necessary for the quick healing of wounds.
While later it was learned that the use of chemical
antiseptics in surgery could be largely replaced by heat
sterilization of apparatus and by the surgical cleaning
of the hands of the operator and by the wearing of a
mask, and so on, still, Lister's work was an immense
advance over old methods either of letting "nature
take its course" or of pouring hot oil on the wounds or
using other barbarous procedures. It is true that long
before Lister's time OHver Wendell Holmes, in America
(1843), maintained that puerperal fever (childbed
fever), that former bane of childbirth, was due to a
virus that might be carried by attendants, physicians
as well as nurses, from patient to patient. And while
he was ridiculed by his colleagues as an immature raver
about a condition that they declared was plainly due to
"Pro\adence," he maintained his contention. He was
soon brilliantly corroborated by Semmelweiss in Aus-
tria (184)7), who showed that if examiners in a lying-in
ward first washed their hands in a chloride of Hme

16 WHOS WHO AMONG THE MICROBES

solution, puerperal fever practically stopped in that
ward. Of course, we know now that the disinfecting of
hands, wliile perhaps the chief means of preventing
puerperal fever and a wonderful advance over the old
custom of merely washing the hands, as was ordinarily
done, even though coming from the dissecting room to
the wards, does not wholly prevent the danger from
the carriers, which we will tell about later.

This skeptical reaction of many of the medical pro-
fession to the brave and logical presentations of Holmes
and Semmelweiss illustrates again how difficult it seems
to be for the majority to break away from custom. Most
of the doctors strongly opposed the communicable na-
ture theory of disease, and it was not until Lister's
time that it was generally accepted.

From the discoveries in rapid succession of the spe-
cific microbes of many of the infectious diseases, and
the demonstration by Pasteur that other vaccines than
that against smallpox might prevent each its own dis-
ease, may be dated the beginning of the fight against
dangerous microbes which constitutes a large part of
modern preventive medicine. Facts in regard to these
later discoveries will be given in the following chapters.

CHAPTER II
HOW MICROBES BECOME BETTER KNOWN

Through the microscope — By the use of stains — By the use of
culture media.

Our chief aid in becoming acquainted with microbes
must be, of course, the microscope. The revelations
through the first lenses spoken of in our previous chap-
ter gave only a ghmpse of the subvisible world that we
know to-day. Through the series of lenses in the com-
pound microscope of to-day the lower limits of vision
are extended about twenty^fold over those early lenses.
That is, we may see germs magnified as much as 2000
diameters, which allows us to distinguish some indi-
vidual characteristics of all but a few of even these
minute beings.

This wonder, the modem microscope, has been
gradually evolved from the imperfectly ground low
magnification lenses of Jansen in 1590, Kircher in
1659 and Leeuwenhoek in 1675. While Leeuwenhoek's
lenses were an improvement over the others, their power
to magnify was not much greater and they were still
full of imperfections that often caused the objects
studied to appear Hke distorted and indefinite dots and
Hues. One has only to visit the Army Medical Museum
in Washington and view their wonderful and fantastic
collection of old microscopes, one of Jansen's time and
a number dating before the time of van Leeuwenhoek,

18 WHO S WHO AMONG THE MICROBES

to realize what improvements have been made. With
the development much later of the Huyghenian com-
pensation eyepieces, the immersion lens, the Abbe sub-
stage condenser with its iris blender, and the series of
finely ground compensation lenses of special glass in
the objectives and eyepieces, our microscopes of to-day
allow us to perceive more or less clear-cut pictures of
all of the known microbes.

A bifocal or binocular microscope adds greatly to
the comfort of the observer. Then there is the dark
field microscope that was invented to help study very
minute particles and so-called ultra-microscopic forms.
These little points of matter catch the obhque rays of
light and reflect them to the eye, thus standing out on
an otherwise dark field.

In order to understand fully the structure and work-
ings of our microscopes, a special book on the subject
should be consulted.^

We may study individual germs through the micro-
scope in either the living or dead condition. Since
through our high-power lenses these minute organisms
w^hen hving appear for the most part only as tiny bits
of translucent jelly-like substances containing one or
more refractile granules, they must be killed, fixed to a
glass slide and stained in certain ways in order to learn
more details of their structural differences and of their
individual reactions to special stains.

Living, the microbes are examined in what is called
a hanging drop of a fluid menstrum, or they may be
planted on a hanging mass of a transparent solid
medium. The hanging drop or mass is placed on the

^One of the good ones is Gage's "The Microscope." Ithaca, N. Y.:
The Comstock Publishing Company, 1925.

HOTT MICEOBES BECOME BETTER KNOWN 19

center of a little square piece of thin glass (cover
glass) and then inverted over a glass shde at the place
where there is a hollow of about a half inch diameter.
The surface of the glass around the hollow is smeared
with a Httle vasehne or other inert oil. Tliis allows the
cover glass to stick after being pressed down and pre-
vents the drj'ing of the drop. In this way we can study
the individual form of the microbes, also their motion,
size, shape, growth, division, spore formation, \'ital
staining, and their reactions to specific serums, such as
the Widal reaction (the agglutination test) and other
so-called serologic tests which we \n\\ explain later.

Fig. 1

HOIiOW SLIDE WITH COrETt-GLASS FOR STUDYING A HANGING DROP OF
GERMS THROCGH THE MICROSCOPE.

To examine the organisms dead they must be spread
in an even film on a glass slide, dried, fixed usually by
heat or alcohol and finally stained. In tissues the organ-
isms must be examined stained in sections.

The microscope and stains alone are not enough for
complete identification of most micro-organisms. We
must use cultural methods as well in order to get pure
cultures of the germs and bring out the mass growth
characteristics of these pure cultures. In order to ob-
tain pure cultures we must get colony gro^^iilis from a
single individual. We obtain these colony growths by
one of two methods. In the first we make high dilutions
of the menstrum containing the germ and mix each in
a transparent jelly medium while it is in a fluid state;
then we pour the mixture into a Petri dish which is
made of clear glass, allow it to solidify and let it stand

20 WHO S WHO AMONG THE MICROBES

at the right temperature for growth. In the other
method we spread the menstrmn thinly over the surface
of a sohd transparent medium in a Petri dish. Each
germ then multiphes many thousand times until there
is a Httle mass gro^vth or colon j^, usually becoming large
enough to be seen with the naked eye. The colonies of
manj'' varieties of bacteria present so characteristic an
appearance on certain culture media that they are of
aid in the identification of the organism. From each of
these colonies a pure culture of the organism may be
obtained by "fisliing" or touching a portion of a single
colony with a sterile platinum needle and transferring
it to a plate or tube of a fresh sterile medium. In many
cases this fishing has to be done under a low-power lens
of the microscope, in order to be sure we have touched
with our fishing needle no other colonies invisible to
the unaided eye (see Frontispiece). The hand of the
*'fisher" must be steady and his eye true to be able to
touch the right colony and only that one.

When we obtain a pure culture we study mass
growth further by transferring the growth to special
culture media that are suitable for showing up differ-
ent traits. In this way we examine types of colonies,
rates of growth, including counting of colonies, effects
on carbohydrates and other substances, and many other
traits.

We see, therefore, that in order to begin the study of
germs we must know first how to use the microscope;
second, how to use stains ; and third, how to make and
use culture media.

As to the use of the microscope, one can only give
here a practical hint or two in regard to focusing.

Different types of colonies of niicTohes from subway air grown
on transparent agar jelly for 24: hours at 36° C. Natural size

HOW MICROBES BECOME BETTER KNOWN 21

The cliief difficulty in focusing is with the higher
magnifications. The objective should be focused down
by means of the coarse adjustment until it approaches
very near to the glass slide containing the object to be
examined, without touching it. Tliis can be observed
from the slide. Then with, the eye at the eyepiece the
coarse adjustment should be moved up slowly and care-
fully until the specimen comes plainly into view. This
focal point may be easily passed if the light is too
intense and the specimen thin and transparent. When
the object is brought fairly well into focus by means of
the coarse adjustment, the fine adjustment should be
used to focus on the particular spot desired. When the
oil immersion lens is used the objective is focused down
until, as observed from the side, it just touches the
drop of oil that has been placed on the specimen to be
examined.

In examining a hanging drop, the diaphragm of the
substage should be nearly closed and the edge of the
drop should be found first with a low-power lens.

The influence of stains on our knowledge of micro-
organisms has been a most important one. The value
of aniHne dyes was discovered quite earty, but it was
not applied to microbes until about 1871, when Wei-
gert and others began staining bacteria, and a few
j^ears later (1877) a whole group of investigators
began making some important discoveries in regard to
the relationsliip of stains to micro-organisms, chief
among them being Weigert, Ehrlich, Gram and Koch.
They found that certain bacteria took different stains
with different degrees of intensity, and that some were
decolorized by certain chemicals and others were not.

22 WHO S WHO AMONG THE MICROBES

So a number of different staining methods were devised
that have been of the greatest aid in detecting and
learning about germs. ^

Practically for the identification of most known
microbes one needs to know only a few staining
methods.

The one that is used most frequently in differentiat-
ing groups of microbes, especially of bacteria, is that
devised by Gram, hence called the Gram method. The
fixed organisms, in spreads or sections, are first im-
mersed for a minute in a strong solution of one of the
more intense stains, such as gentian violet which has
been made even more effective by the addition of a
substance called a mordant, hke aniline water. Then the
preparation is placed for thirty seconds in some de-
colorizing solution, like alcohol. About half of the
microbes have all of this intense stain removed by the
alcohol, while most of the rest retain the stain and
appear under the microscope as dark blue or violet
germs. The remaining microbes show varying degrees
of decolorization. To make those that are decolorized
stand out more plainly we finally immerse the prepara-
tion in another stain of contrasting color like the red
fuchsin in weak dilution. Those that retain the first
stain after treatment with alcohol are called Gram-
positive organisms, while those that lose it are called
Gram-negative organisms. Those that only partly re-
tain the first stain are called Gram-amphophile germs.

The single stain that is most used in practice is one
called alkaline methylene blue. When alkah is added to

' Such work as Lee's "Vade Mecum" should be read by those who
want to learn more about this subject. Published by P. Blakiston's
Sons, Philadelphia, 1928— 9th ed.

HOW MICROBES BECOME BETTER KNOWN 23

a solution of methylene blue and the mixture allowed
to stand for some time, part of the stain is converted
into methj'lene azur, wliich gives certain granules in
some microbes a reddish appearance, while the rest of
the organism stains a blue. Diphtheria bacilli are
easily spotted by this stain.

Then, certain bacteria, like the tubercle bacillus,
and also the spores of bacilli, are so difficult to stain
that a strong solution boiling hot must be used ; but
once stained, they retain the stain even after they are
immersed in acid solutions. Such bacteria are called
acid-fast organisms.

Special staining methods must be used to demon-
strate the capsules that envelop certain organisms, and
very special methods must be employed to show those
extremely deHcate hairhke appendages, called flagella,
that motile organisms possess.

The use of culture media in our study of microbes
is of course indispensable.

It was earlj^ observed that most microbes grew well
in various liquids, such as milk, meat infusion, sputum,
blood, grape juice, grain infusions, and that they also
grow well on sohds, such as cheese, shced potatoes,
bread, jeUies, fruits, eggs and others; but it was not
until methods were devised by Psisteur, Hess, Koch and
others for obtaining pure cultures of individual varie-
ties of germs, that knowledge of the kind of culture
media best suited for the different varieties of microbes
was obtained.

Before we can make culture media we must know
about getting everj'tliing we work with free from germs
— that is, everything must be sterilized. Not only that,
but we must be sure that all of the glassware we work

WHO S WHO AMONG THE MICROBES

with is reasonably free from acids and alkalis. In order
to rid them of these foreign disturbers, each piece must
be neutralized and washed in a special way. And the
plugging! This means an enormous amount of work
in a large laboratory. All narrow-mouthed containers

LIGHT SOURCE

EYE

Fig. 2

Comparator Block : A, mbdidm + indicator ; B, water : C, medium
+ NO indicator; D, standard solution + indicator; E, slit for

OBSERVATION.

used — and there are thousands of them in the larger
laboratories — must be plugged with non-absorbent cot-
ton before they are sterilized. This is to protect the
interior from contamination, since microbes cannot pass
through dry cotton.

A big force of laboratory helpers must be employed

HOW MICROBES BECOME BETTER KNOWN 25

in doing only the work of getting the apparatus ready
for culture media. The glassware is all sterilized in dry

Fig. S
Diagram of inxer consteuction of horizontal autoclave. A,

PASSAGE FOR STEAM FROM JACKET TO CHAMBER ; B, SOURCE OF HEAT IF
GAS IS USED.

heat ovens at a very high temperature (175° C. for two
hours), so that the most resistant spores that some-
times occur may be destroyed. (See plate opposite
p. 27.)

It was found that the best culture media for the

WHO S WHO AMONG THE MICROBES

largest number of species was a clear meat infusion

broth made very much as our cooks make meat broth

for our dinner-tables.

We know that beef hearts (what an opportunity for

sentimentalists to protest!) make one of the best in-
fusions for our microbes.
To this infusion we add
a little salt and a small
amount of a specially
prepared peptone, which
is a partially digested
protein.

The reaction (alkaline
or acid) of this broth is
a very important matter.
While most microbes
grow well in a culture
medium that is neither
acid nor alkaline — that
is, one that is neutral —
some grow best when the
medium is a little alka-
line, some when it is a
little acid. So each lot of
broth is very carefully

adjusted for the kind of microbe that is to be grown

in it.

We determine these reactions by a special electric

apparatus or by a set of colored fluids in test tubes held

in what is called a comparator block (colorimetric

method). (Seep. 24.)

This broth is strained to make it clear and then it is

poured into sterile containers and steriHzed at a definite

Fig i
Arnold steam sterilizer.

HOW MICROBES BECOME BETTER KNOWN 27

heat, according to the composition of the culture
medium and the use to which it is to be put.

The sterihzation of media is made in one of two
kinds of steriHzers. As a routine we use an autoclave.
This is a very strongly built sterilizer, where the steam
heat can be increased by means of pressure. We usually
use fifteen pounds pressure for half an hour. Some
bacteria grow best in a culture medium that has not
been subjected to such great heat. For these we use the
Arnold sterihzer. At the low heat of the Arnold (about
99° C), spores are not readily destroyed, so we must
expose the culture medium to this heat for half an hour
on three successive days, leaving it at room temperature
between times. This gives a chance for any spores that
may be present to develop into vegetative or young
non-sporulating forms, when they are easily destroyed
by that heat. When the broth is ready for use it is called
nutrient broth. It is not onlj^ a good medium in itself
for most bacteria, but it is the basis of most of the
special culture media that are used for growing the
more exacting microbes or growing them for special
purposes.

One of the most important additions we make to this
nutrient broth is something which will produce a sohd
transparent medium that allows germs to grow in sepa-
rate colonies.

It Avas first found that gelatine was a helpful sub-
stance to use. It is fluid when warmed and solid when
cooled, so germs can be mixed with it in a fluid con-
dition ; and when it was allowed to sohdif y, all the
germs that would grow at the temperature of solidifica-
tion would grow in Httle colonies, each one separated
from the other. But since gelatine melts at the tempera-

28 TTHO S WHO AMONG THE MICROBES

ture best suited for the growth of most pathogenic
germs, this was only a partial help. It does allow, how-
ever, certain germs to grow in it in a very characteristic
way, and so its use was considered an important differ-
ential method until other more significant methods were
learned. Its Uquefaction by certain germs is still used,
hoAA'ever, as an aid in classification.

The unsatisfactory characteristics of the animal
gelatine were replaced by the very adequate agar agar,
a gelatine made from species of algae in Japan. Tliis
forms a very stiff jelly that does not melt under a tem-
perature of 80° C. or more, but when melted does not
become solid until it drops to about 36° C.

To these solid nutrient media and to the nutrient
broth many different substances may be added to en-
rich, to differentiate the species and to aid in diagnostic
measures ; for different germs utihze different sub-
stances or change them in different ways.

Studying these minute beings called microbes
through the microscope, living or non-h%'ing, unstained
or stained, singly or in masses, in their natural en-
vironment or in artificial cultures, we find that they
can be divided into three large classes, the bacteria or
lowest plants, the yeasts and molds or next higher
plants, and the protozoa or lowest animal forms.

These three have been grouped together by some
biologists under the name Protista, which means the
very first.

Often the term bacteria is loosely used to designate
the whole group. The name parasite, which is also ap-
plied to the whole group, is not a good general name
because many of the forms are not parasitic. Either of

Worker using fermentation tube containing sugar broth for growing
microbes, to show their powers to produce acid and gas and grow
without air

Corner of media room showing uorkcr-, j)rfi)aring glassware to be
sterilized in hot air sterilizer, at right. The large flasi<s containing
nutrient broth have just been taken from autoclave, at right
foreground

Some types of the three great classes of microbes. Top row shows
bacteria-!-cocci, bacilli and spirilla. Middle row shows yeasts and
molds. Bottom row shows protozoa — flagellates, amebas and blood
sporozoa. Magnified about 1000 diameters. (From Kolle and
Wassermann, except 4, 6 and 8; 6 is from Fraenkel & Pfeiffer.)

HOW MICROBES BECOME BETTER KNOWN 29

the terms microbe and germ is better as a common
general name.

Each of these groups has certain general qualities
or characteristics which distinguish it from the others,
though its border numbers may show some relations to
those of the other groups.

First there are the bacteria. The bacteria are con-
sidered the simplest of all known living beings. The
individual bacterium has no partitions — that is, it is a
single cell surrounded by a dehcate membrane, like a
sausage in a sack. It contains no formed nucleus, as do
the cells of most higher plants and animals.

Each bacterium usually contains from one to many
minute granules, some of which are composed of nu-
clein, an albuminous material that is found in nuclei of
higher forms. Some of these granules are so definitely
arranged and stain so distinctively that, if the bac-
terium has been fixed and stained in the right way, one
may know to which family it belongs the minute one
sees it under the microscope. We can spot some po-
tentially pathogenic forms in this way, and so make
use of this method to detect them in our diagnostic
laboratories. These granules vary in size and coloring
according to the age of the bacterium.

At a definite age in the life of a few types of bac-
teria, mostly found in soils, some of these granules
fuse, producing a rounded glistening body surrounded
by a thick tough membrane which makes it very re-
sistant to outside influences. These resistant bodies are
the so-called spores, seeds or reproductive bodies, about
whose discovery we have spoken in our sketch of early
discoveries (Chapter I) and whose interference with

30 WHO S WHO AMONG THE MICROBES

the sterility of our culture media we have just men-
tioned. We have also called attention to the difficulty
of staining them and consequently of the very special
staining methods we must use to demonstrate them in
this way. They are resistant in a varying degree to
heat, drying, light and chemical disinfectants. They
may lie quiescent (hybemating) for ages, and then
when placed in favorable culture media they swell,
burst their tough membrane and grow out again to an
adult bacterium — the so-called vegetative form. The
position of these spores helps in the identification of
some forms. Thus, some develop at the end of the
bacillus, forming a head like a drumstick; in other
species the spores form in the middle of the rod, often
making a spindle shape; in others it forms between
the center and the end of the rod.

The formations of these spores are said to be nature's
simple method of protecting this kind of bacteria
against adverse conditions. It is certainly an effective
method against many harmful conditions that the
germs may meet in the soil which is their natural home.
A comparatively few pathogenic microbes are among
these marked spore-bearers. Some bacteria that have
none of these resistant kinds of spores still have the
power to exist in a quiescent state, under certain con-
ditions, for a variable length of time.

The motile bacteria have very fine hair-Hke ap-
pendages, called flagella, which help the Httle creatures
to smm about. When viewed under the microscope some
of the motile ones seem to be moving very quickly —
and, taking their size into consideration, they do. If
man were to move as fast in proportion to his size he
would go a mile a minute. INIeasured by our time they

HOW MICROBES BECOME BETTER KNOWN 31

move slowly. It has been estimated that the cholera
spirillum at the height of its activity may travel at the
rate of eighteen centimeters (seven inches) in an hour.

It is almost impossible to conceive of the size of one
of these minute Hving organisms. To give some idea,
we may use some such series of comparisons as follows :

The ordinary high-power lens that we use magnifies
about 1600 diameters. A pea one quarter of an inch in
diameter if magnified to this extent would look as large
as a house about a thirty-three-foot cube. The pea has a
diameter about 900 times the length of a tubercle bacil-
lus. If an influenza bacillus, one of the smallest we can
see, could be magnified so that it would appear two
inches long, an ordinary sized pea magnified in pro-
portion would have a diameter of almost three times
the height of the Washington Monument, or in other
words it would be as wide as the length of seven city
blocks.

Let us continue the comparison. The unit of bacterial
measure is one micron or /4 5,000 of an inch. The Greek
letter [i is used to designate the term micron. An aver-
age sized influenza bacillus wliich is one [i long is one
eighth of the diameter of a red blood cell, which is
eight [1, or about /4.200 of an inch. A small mustard seed
is about one twentieth of an inch. Under a lens magni-
fying 100 diameters one can just make out the red
blood cell and a section of the circumference of the
mustard seed (Fig. 5). According to Peabody and
Hunt, 1,500 typhoid bacilli arranged in procession end
to end would scarcely stretch across a pin head. Kendall
estimated that the weight of ten millions of millions
would scarcely equal an ounce.

The growth and division of these minute creatures

32 WHO S WHO AMONG THE MICROBES

RED BLOOD CELL
32^qINCH diameter

ENLARGED 100 TIMES

RED BLOOD CELL, Sufi^oo 'NCHJ

' DIAMETER

— INFLUENZA BACILLUS, I u (^g^oS 'NCH)

LONG
ENLARGED 2000 TIMES

COMPARATIVE SIZE OF BACTERIA

Fig. S

- ^

1 '"'

* 1

• •

'X,

;fr

« cvr^' • >

C-J.

c<r

«>

^A,

Certain parts of bacteria. Top row shows capsule^ of l)acilli and
cocci. Middle row shows flagella of bacilli and spirilla. Bottom
row shows spores, in the first growing at the end of the bacilli,
in the second near the middle of the rod and in the last the
living spores show in threads of bacilli

Anthrax bacilli growing in spleen of mouse and showing a capsule.
Enlarged 1300 diameters

HOW MICROBES BECOME BETTER KNOWN 33

may be observed, if one has patience, under the micro-
scope. We have watched for hours the growi;h of the
diphtheria bacillus and seen the rather startUng snap-
ping of the dividing bacilU, usually not in the center as
others claim, but nearer one end. The majority of
germs, however, divide at or near their middle.

The rapidity of gro\\i;h varies with the kind of
microbe and with the encouragements or hindrances it
may encounter as it grows. As the average microbe is
said to need only fifteen minutes to divide into two
daughter microbes, we can see that with unrestrained
growth microbes even in so short a time as twenty-four
hours might multiply to an astounding number. But
fortunately for us, this continued vigorous grow'th sel-
dom occurs. Checks to growth are met with on every
side: food supply gives out, waste products accumu-
late, other microbes interfere, the body cells of animals
they may attack react and produce substances that may
kill them, and other factors all aid to check this mad
rush of microbes to increase the numbers of their
progeny.

Grouping the bacteria according to their shape, we
find they are divided into minute balls or berry-hke
forms called cocci, minute rods, or elongated sacs, like
sausages, called bacilli, minute parts of spiral rods
called vibrios. Then there are more definite longer
spirals called spirilla and spirochetes. Finally, there
are thread-like forms with branches called higher bac-
teria because they resemble the molds. These different
characteristics help to divide them into families which
will be described later.

There is no one distinctive characteristic that sepa-
rates these low plant forms from the simplest animal

S4 who's who among the microbes

forms, but when a form shows somewhat more com-
pletely its abihty to grow into filaments and branches,
with definite partitions as in the molds, it is placed in
the next higher plant class; wliile if it shows a more
definite nuclear apparatus with a more plastic body
and with more complex reproductive powers it is placed
with the protozoa.

The molds, including the yeasts, are very common
in nature, and the characteristic ones are easy to recog-
nize and place. But there are many varieties of this big
group that have not been minutely studied, so there is
still great difficulty in classifying them. A number of
them have sexual phases in their growth. They all form
spores that are quite resistant to drying, and as the
spores of many varieties germinate when only small
amounts of moisture and food material are present, a
moldy condition often prevails.

It is interesting that wliile not many pathogenic
yeasts or molds are known, one of the first diseases in
which a micro-organism was found was one caused by a
mold. Schoelein found it in 1839 in a disease of the
scalp called favus; in which little yellow cups of the
mold grow around the base of the hairs. Shortly after
this Langenhock discovered the thrush parasite, which
is a yeast-like mold that so often grows in white patches
in babies' mouths.

The yeasts, or budding microbes, usually have a
very refractile membrane which is easily identified
under the microscope. While most yeasts are larger
than most bacteria, a filterable form has recently been
reported by Lewis. This is e\ddence, of course, that
very minute forms of this kind of microbe exist.

The majority of yeasts and molds grow easily on a

HOW MICROBES BECOME BETTER KNOWN 35

food medium containing a little sugar and that is not
too alkaline, but some of the pathogenic forms, espe-
cially of yeasts, seem very un^-ilHng to start growing
on artificial media. Once started, they too grow readily.
On the whole, molds prefer a shghtly acid food medium.

The yeasts in general stain readily, and are irregu-
larly Gram-positive and Gram-negative (amphophile).
The molds usually require special handhng before they
can be stained. Then they also are Gram-amphophile.

The protozoa, because of their larger size and more
differential structure, are usually more easily studied
under the microscope, but they are more difficult to
grow in pure culture. Few accommodate themselves to
the ordinary laboratory culture media. Quite special
media must be used to obtain satisfactory growths.
These will be described later.

Though the protozoa are larger and show more
structure, most of them pass through such a complex
life cycle, often part of it in a different kind of animal
from the original host, that unless the whole cycle is
known individual forms may be very difficult to classify.
Thus a flagellate form found in a mosquito may be a
stage in the hfe history of the ameboid malarial para-
site found in the blood of human beings. Their study is
further compKcated by their having sexual and asexual
phases.

While most protozoa are much larger than most bac-
teria, there have been forms described that are small
enough and plastic enough to pass through some of our
finer filters.

CHAPTER III
HOW MICROBES LIVE AND ACT

How they behave under different conditions — Helpful, harm-
less, harmful activities — How they are carried to indi-
viduals and from one individual to another.

Microbes are almost ubiquitous. Members of each
class may be found all over the known world. As long
as a trace of organic substance of the simplest nature
and a httle moisture are present, germs of some sorts
may grow. They must all find at least the elements,
nitrogen, carbon, hydrogen, oxygen, phosphorus and
sulphur, but some can make use of them even in their
elementary form and others require all grades of com-
binations. Most varieties need very complex food.

There are kinds that can grow on snow, and kinds
that grow in hot springs ; but only a few varieties can
grow at such extremes. Some varieties have been found
by polar explorers as near the Poles as man lives, while
in the tropics many varieties are found in great abun-
dance. They are found in the ocean, in the air and in
the upper layers of the soil. Indeed, the upper eight
inches of soil constitute perhaps the greatest breeding
place for many microbes. They grow easily, multiply-
ing exceedingly under favorable conditions, but then,
fortunately for us, most of them die easily under un-
favorable conditions.

Little wonder that many varieties of microbes have

HOW MICROBES LIVE AND ACT 37

been evolved through the ages when they evince such
abihty to grow under so many different conditions,
their power to adapt themselves to their surroundings.
There are not only the kinds that grow best with the
simplest food, or with the most complex food; those
that can live best at high temperatures or low tempera-
tures ; but there are those that carry on their lives best
under more special conditions. Indeed, some will not
grow at all unless certain factors are present or absent.

For example, there are those that grow only in the
presence of free oxygen and those that will not grow
unless free oxygen is removed ; there are those that feed
on certain sugars, others that feed on none; those that
Hke to live on or in human beings or other animals, or
those that choose plants for their homes. There are
even some that are so fastidious in their tastes that they
grow only in certain species of animals or plants.

Germs have been given special names to designate
their behavior toward their surroundings. These names
are often high sounding, though their meaning may be
simple enough. Thus, those microbes that seem to
depend only upon a living host for their existence are
called pure parasites ; those that grow only on non-
living food are called pure saprophytes if plant germs
or pure saprozoa if animal germs. Those that have the
faculty of growing either on living or on dead matter
are called facultative saprophytes or saprozoa.

Those germs that grow best at low temperatures
are called psychrophiles or lovers of the cold. The red
and the blue snows, which for a long time seemed so
mysterious, are caused by germs of this kind that
produce either a red or a blue pigment. Many of the
germs that grow in the cold water of the ocean belong

38 WHO S WHO AMONG THE MICROBES

to this group. All forms that grow only below 30° C.
are placed in this group. The temperature the majority
like best — that is, their optimum temperature — ^is
18° C.

Those germs that grow best near the temperature
of the human body are called mesophiles or lovers of
the moderate. The pathogenic germs of human beings
belong in this group. Temperatures a little above or
below this blood heat may have a marked inhibitory
effect on their activities. In order to keep our cultures
of poisonous germs at this equable heat we use special
incubators.

Those that grow at higher temperatures are called
thermophiles or lovers of the heat. They grow best at
about 50° C. They are found chiefly in the soil and in
the alimentary canal of some animals. Some are found
in certain hot springs with a temperature of 140° to
170° F. Ordinary plant or animal life could not live
at this temperature. Some of these thermophiles make
great difficulties in the pasteurization of milk where
long runs are made. They increase as the others
decrease.

While germs cease all movement and growth at un-
favorable temperatures, they are not so easily killed
by cold as they are by heat. Only a comparatively few
degrees of heat will kill most forms in a short time,
while many degrees of cold applied for a long time
are required to kill the majority of the varieties. Thus
fresh ice may contain a large number of germs, while
older ice may have few or none. Alternate freezing and
thawing is more detrimental than continued freezing.
The age of the germs and the media in which they are
growing influence to some degree the effects of heat and

HOW MICROBES LITE AND ACT

cold. Older microbes immersed in
an albuminous or an oily sub-
stance are much more resistant to
heat or cold, either continuous or
alternate, than are those not so
surrounded.

The fact that so few microbes
of any kind, especially disease-
producing microbes, live at the ex-
tremes of temperature has led to
the use of methods for the preser-
vation of foods in which the ap-
plication of either heat or cold is
used. That useful method of keep-
ing doviTi microbal gro"«i:h, called
pasteurization in honor of Pasteur,
developed from our knowledge of
the deadh'^ effect of heat on germs.
This use of moderate heating has
developed into a great industry in
the pasteurization of milk.

Those that require the air or
free oxygen are called aerobes;
those that do not, anaerobic. Those
that can Hve either with or without
free oxygen are called facultative
aerobes or anaerobes. We have
special methods of growing our
anaerobic microbes.

Microbes pathogenic for man as
well as some saprogenic forms do
not like certain of the sun's direct
rays. The rays at the ultra violet

Fig. 6

BUCHNEE'S ANAEROBIC

TDBE. The fluid con-
sists OF PTROGALLIC
ACID DISSOLVED IN 10
PER CENT. NaOH SOLU-
TION. By Wilson's

METHOD THE TUBE IS
CHARGED WITH PIBCES
OF CAUSTIC POTASH COV-
ERED WITH PTROGALMC
ACID.

40 WHO S WHO AMONG THE MICROBES

end of the spectrum have a kiUing power over most
of the pathogenic forms. Window-glass will absorb
these rays; quartz permits them to pass.

The tubercle bacillus particularly has been under
observation as regards the sun's rays. It has been found
that in the presence of abundant oxygen and sun's rays
the germs in sputum may be killed in a few hours.

The inhibitory effect of direct sunlight on certain
bacteria may be easily demonstrated by mixing the
bacteria into a jelly medium when fluid, such as warm
nutrient agar, and pouring the mixture into a series of
quartz Petri dishes, then covering a part of the cover
with a strip of black paper. These are then exposed to
the sun's rays for a variable time and put at the proper
temperature for growth. After a certain exposure
colonies of the germs will appear only over the pro-
tected areas.

Radium rays and electric rays also have a kilhng
effect on microbes directly exposed to them.

The study of the effect of electric charge or the
electric potential difference between a germ and its
menstrum may lead to new methods of recognizing
specific varieties. Falk ^ has summed up the recent
studies on this suggestive subject and outHned a theory
of microbic virulence.

The influence of direct pressure upon microbes has
been found to be shght so far as their destruction is
concerned, but the influence of differences of pressure
between the culture medium and the germs — the so-
called osmotic pressure — is of great importance upon
the growth of microbes. Upon osmosis depends largely

* "The Newer Knowledge of Bacteriology and Immunology." Ed.
by Jordan and Falk. University of Chicago Press, 1928.

HOW MICROBES LIVE AND ACT 41

the growth of all germs. The difference in pressure be-
tween the cell and a new medium must not be too great
or the cell may either swell and burst or become
shrunken and dried in its efforts to estabhsh an
equihbrium.

Thus, if a strong salt solution is added to a collection
of microbes, the water in the germ cells will be attracted
to the salt and will pass out of the porous membrane
enclosing the cell and mix with the salt solution. De-
pending upon the amount of salt and water, a certain
amount of salt may pass into the bacterial cell until
the pressure is equalized. In the process the germ
ceases to grow, and it may actually die. A practical
apphcation of tliis principle is known as pickling or
corning.

Strong sugar solutions have the same effect and are
also used to preserve foods from the growth and dele-
terious effects of microbes. Tlie Frenchman Appert
used this principle long ago in the preserving of fruits.

The inliibiting effect of drying upon microbes was
used in practice long before it was known that microbes
existed. Meat and fish were and still are preserved by
the process of "jerking." Tliis is simply the cutting of
the fresh meat and the hanging of it in the sun to dry
after cutting the larger portion into thin strips. Now
desiccation is practised in the industries on a large
scale. Desiccated fruits and vegetables, desiccated meats
and fish, desiccated milk are all well preserved and on
the market.

Microbes growing together may have a marked effect
on each other for good or for evil. Certain products of
the gro\\i:h of one may help directly the growth of an-
other, thus acting as a vitamin. For example, the influ-

42 WHOS WHO AMONG THE MICROBES

enza bacillus will not grow alone unless blood or certain
vitamin-like substances from different vegetables are
mixed with ordinary culture media, but it will grow on
ordinary media in mixed cultures T\4th certain microbes.
This is called symbiosis, though it is not symbiosis
according to the strict meaning of the word. Some
microbes, however, grow in true symbiosis with certain
plants. On the other hand, certain germs are antago-
nistic to each other.

Certain germs, even harmful under some conditions,
may grow on the surface of man's body without doing
it any apparent harm. These are the so-called parasitic
forms. While these germs may not be harmful to the
human being carrying them because he may not be
susceptible to them, they may be transmitted to other
people coming in contact with the secretions or excre-
tions containing these germs — e.g., saliva, through
kissing; and if people are in a susceptible condition
they may come down, with the disease.

People apparently normal who harbor germs of
potential pathogenic power are called human microbe
carriers or human vectors. It is in this way, by the
human carrier, that certain diseases continue to be
spread. Fortunately for us, pathogenic germs, as a
whole — that is, those that are liighly parasitic — do not
exist for a long time outside of the animal body, except
under very favorable conditions. When expelled and
exposed to the natural germicidal agencies of sunhght
and desiccation only a few may reach a new host. This
is our salvation. Spore-bearing forms and any faculta-
tive parasites are exceptions to this rule. The closer
the relationship in time and space to the source of
infection, the greater the chance of successful transfer

HOT\- MICROBES LITE AND ACT 43

of ^-irulent infective agents. Germs have become adapted
to escape by the natural avenues used for the physio-
logic discharge of secretions or excretions of the body
— that is, the sputum, feces and urine. The easier the
avenues of escape from the host, the greater the num-
ber of germs that infect a new host. Those infectious
germs that can readily reach and infect a new host are
called contagious. All germs that are poisonous for
man are called infectious; only a few of these are
labeled contagious.

The carrier may have contracted the carrier state
after a regular attack of the disease, when he is called
a convalescent carrier ; or if he has some immunity when
he takes in the germ after contact with one who is har-
boring it, he may become a carrier \^'ithout contracting
the disease. In tliis case he is called a normal or a con-
tact earner.

Carriers are called transient or temporary if they
have the germ for only three months or less. If they
harbor the germ longer, they are called chronic carriers.
The carrier may be more dangerous as a power of
infection than an actual case, because he may live un-
suspected in a community.

Some germs spend part of their lives in each of two
hosts. Bacteria for the most part are only adventi-
tiously carried by lower animals. Thus the house-fly
may carry typhoid bacilli on its legs after walking
over infected feces or other infected material. Protozoa,
however, have the faculty of carrying on part of their
hfe cycle in a lower animal, usuall}' an insect carrier
or vector, such as the mosquito in malaria. Such a lower
animal may be the real or definitive host of the germ,
and the higher animal the intermediate carrier. Some

44 WHO S WHO AMONG THE MICROBES

pathogens for man have a higher animal as a natural
host — for example, rabies in dogs.

Germs in their growth not only manufacture prod-
ucts that have helpful or harmful effects on each other,
but they form products some of which, as we have said,
are helpful, even essential, and some harmful to man.
The power of microbes to do this depends upon many
factors, to some of which we have alluded.

To tell all we know in a book of this size about the
helpful and harmful products of microbal growth will
be impossible. We can only touch here and in later
chapters on the more important ones that occur in the
industries and in disease. The influence of many of these
factors may be readily shown in the laboratory. Thus,
the diphtheria bacillus has the power to produce a very
potent toxin wliich can kill human beings quickly if it
meets with no obstacles.

The discovery that this toxin could be produced in
the laboratories was made many years ago by two
Frenchmen — Roux and Yersin. That was a wonderful
discovery. Their original method of manufacturing tliis
toxin, due to their knowledge of only a few of the
factors influencing its production, was long and com-
plicated. They used large flat flasks, containing only
a little of the culture medium, each flask connected in
series to cylinders of oxygen gas. The gas was drawn
through the flasks by a suction pump. It was thought
that oxygen helped the gro^^i:h of the bacilli and their
production of toxin. The bacilli were kept in this con-
dition for about six weeks.

This was the lengthy and cumbersome method that
was still being employed when we started our investiga-
tions on the best method of producing this toxin. We

HOW MICROBES LITE AND ACT 45

quickly made some discoveries in the New York City
Health Department laboratories that altered our ideas
as to how best to make this toxin.

In the first place, we were fortunate enough early to
find a strain of the diphtheria bacillus, among the many
we tested, that produced, under the right conditions, a
very strong toxin. We found, further, that neither this
strain nor any other we tested needed the stream of
oxygen to make it produce good toxin ; moreover, we
found that the toxin appeared in largest amounts in
about six days instead of six weeks.

We found also that the reaction of the culture
medium was of the greatest importance. If the medium
was a little too acid or too alkaline, no toxin or very
Httle would be produced. So on the addition of a
certain amount of sugar to the medium, the bacilh in
their growth may produce no toxin.

It is a commentary on our lack of knowledge of these
mj'sterious creatures that, notwithstanding our taking
advantage of these and other new facts learned by
investigators throughout the world, we still get variable
results in trying to produce good toxins for the manu-
facture of antitoxins and for the vaccines used to pro-
tect children against diphtheria. We have found re-
cently that these bacteria as well as all others we have
studied tend to change and produce non-toxic varieties,
and we are learning how to keep the toxic varieties in
full vigor.

The kind of a toxin produced b}^ the diphtheria
bacilli is called an exotoxin, because it is found in the
culture medium outside of the bodies of the bacteria
themselves as a result of their gro\\i;h. Toxins of this
nature have the power, under appropriate conditions,

46 WHOS WHO AMONG THE MICROBES

of stimulating in the susceptible animals injected with
them substances that counteract the poisonous effects
of the toxin, the so-called antitoxins, which will be de-
scribed in the next chapter.

The outstanding toxins of this type are only four,
diphtheria, tetanus, botuHnus and scarlet fever. Their
traits will be taken up in later chapters.

There are a number of other extracellular products
of a similar character that have various effects upon the
medium in which they grow. They are called enzymes or
ferments, and they produce reactions such as coagula-
tion, liquefaction, digestion, decay, putrefaction, sugar
and fat sphtting, and so on.

Many of these reactions are essential in the cycle
of life. Some of them are taken advantage of in identi-
fying closely related microbes and are used to detect
epidemic strains.

The most striking characteristic of microbes is their
individuahty combined with their variability. If we
were able to learn all the traits of each individual
microbe and how these traits varied under different con-
ditions, we would no doubt find an individuality and a
variabihty comparable to those we observe among more
complex li\'ing forms. The progeny of each microbe
exhibits, for a time at least and under similar condi-
tions, the traits of its ancestors. This individuality is
called specificity. Many species of microbes have such
specific individual traits that they may be recognized
more or less easily by their characteristic growths and
reactions in different culture media, including their
growth in the body of a living host.

One of the most important types of substances used
by microbes as well as by man in their growth is that

HOW MICROBES LIVE AND ACT 47

known as carbohydrates. Carbohydrates are the chief
source of energy of Hfe. They comprise the sugars,
starches and related forms. There are hundreds of them,
some well kno^Ti to us, such as cane-sugar, grape-sugar,
milk-sugar; others known to chemists and microbi-
ologists as important chemical reagents. Certain
microbes ferment certain of the sugars, others few,
others one and others none.

In using the sugars for testing the relationship of
microbes one must be very sure of their purity. We
make the final test by using known microbes that may
detect the smallest quantity of a particular sugar, so
we alwaj's have a number of control tubes implanted
M'ith different test microbes whenever we make a sugar
test. Microbes are among the most delicate and specific
testers of sugars.

Some microbes spHt up the sugar with the produc-
tion of acid and gas, others onl}^ with the product of
acid. We use a special bent tube with one end closed
when we wish to show the presence of gas.

The presence of acid is demonstrated by putting
into the test medium a substance that will chang-e color
if the germs split up the sugar with the formation of
acid. Such a substance is called an indicator. The chief
ones used by microbiologists are litmus, phenolphthal-
ein and certain dyes decolorized by sodium hj'droxide,
or reduced by sodium sulphite.

A rather complex series of media of this type that is
very satisfactory is used in demonstrating the presence
of different members of the intestinal bacteria, the so-
called typhoid-coli-dysentery group.

There are a number of other products of microbal
growth classed among the enzj^mes that have a marked

48 WHO S WHO AMONG THE MICROBES

effect upon different cells. Some cause a breaking up or
dissohdng of red blood cells. These are called hemo-
lysins. Others affect other cells. They may all be classed
under the general name cytolysins, or cell dissolvers.

Besides producing these exoenzymes and exotoxins,
some micro-organisms have the power of injuring the
tissues of their hosts by growing directly in and through
them. The germs either release a poison as they die
(endotoxin), or they use certain parts of their hosts'
cells for their food and thus destroy the cells directly ;
or they form a poison out of this new combination of
bacterial activity and cell breaking up. All of these
poisonous effects are said to be due to endotoxins.

Whatever the nature of this poisoning, the chief
practical point is that, when susceptible animals are
injected with non-lethal graduated doses of such micro-
organisms, specific antibodies or counter-poisons ap-
pear in the serum of the injected animals.

These antibodies are quite different from the anti-
toxins stimulated by the exotoxins. They are more
complex. They will be described in the next chapter.

Among these substances is one that still remains a
great mystery, though many studies have been made in
attempts to discover its true nature. This is the famous
"bacteriophage" of Twort and d'Herelle. We don't
yet know whether it should be described here as a toxin-
like ferment, or be put w^th the filterable viruses as a
living entity. Some writers declare that it is one, some
that it is the other.

Here is the story of its discovery, and the little evi-
dence we have in favor of each view.

In 1915 an Englishman of the name of Twort, while
searching for the cause of vaccinia (cow^ox), noticed,

HOTV MICROBES LITE AXD ACT 49

in some of the dense colonies of bacteria groAnng on
the nutrient agar culture medium he was using, some
translucent or watery looking areas. The colonies in
which these areas had advanced farthest could not be
subcultured, and if left long enough the whole colony
would become translucent. If a small portion of such a
glassy colony was touched to a pure culture of the same
type of bacterium as that in which they had appeared, a
spreading, translucent area started, and soon the whole
culture might be changed and become incapable of
being transferred ; that is, it was dead.

This power to change the growing culture to a dead
glassy mass, was possessed b}^ filtrates of this trans-
lucent material. The active principle passed through
the finest porcelain filters without any apparent loss
of activity.

Twort thought that this active agent might be a
living filterable virus, but he favored the hypothesis
that it was an enzyme derived from the bacteria them-
selves.

No attention was paid to this work until 1917, when
the Frenchman d'Herelle announced as a new discovery
that he had found a living, ultra-microscopic organism
that killed certain bacteria. Wliile d'Herelle was at-
tempting to discover the cause of the disappearance of
the dysentery bacilli from the feces of convalescents, he
found that minute quantities of fecal filtrates of such
patients inhibited the growth of dj^senterj'^ bacilli in
cultures. He found, just as Twort had, that this l^'tic
power could be passed on from culture to culture in-
definitely— indeed, that it seemed to become more active
the longer it was transferred.

D'Herelle beHeved then, and he still strongly be-

50 WHO S WHO AMONG THE MICROBES

lieves, that this phenomenon Is due to a Hving, multi-
plying ultra-microscopic microbe that destroys certain
bacteria. He has even given it a name. He calls it Bac-
teriophagum intestinale.

Which idea is right? In their search for an answer
to this question many new facts have been discovered in
regard to this phenomenon, but the question has not
been settled yet.

It has been discovered that many bacteria are sub-
ject to this phenomenon. Almost every bacterium
studied from infected material seems to have an associ-
ated phage. While the evidence is in favor of each
phage being specific for each micro-organism or group
of micro-organisms, this too is not proved.

Each evidence that is brought forward in favor of
a phage being a living principle is shown by the op-
ponents not to have been sufficiently controlled. One
should read Bronfenbrenner ^ to get a summing up of
both sides, and the latest researches on this subject.

The questions of resisting cultures, of the produc-
tion of antiphage, and of the significance of phage in
infectious diseases, are all of the deepest interest.

According to d'Herelle and others, phage may play
a very important part in the cure of certain diseases.
Good results have been reported by some in staphylo-
coccus infections such as boils, in dysentery, in cholera
and in a few other diseases. Others have not been able
fully to corroborate these results.

*In "Filterable Viruses." Ed. by Rivers. Baltimore: The Williams
& Wilkins Company, 1928.

CHAPTER IV
HOW NATURE REACTS TO MICROBES

Limitations of nature's methods — Man's assistance — Natural
and acquired immunity to poisonous microbes.

"Let nature take its course"; "Do not interfere with
nature's plan," or a similar cry is often heard from
some slogan crier among the superficial observers who
are all too frequently heard in this easy-going world of
ours. Such people do not realize that there is no clear-
cut dividing line between man and the rest of nature,
that man's attempts to regulate the waj^s of the
microbes is a part of nature's general scheme ; in other
words, that man himself is one of nature's forces. We
want to show, therefore, in this chapter how nature
reacts in this broad sense of the meaning of this phrase.

Let us rehearse first what might happen if we should
"let nature take its course" according to the way these
narrow "naturalists'* interpret the meaning of the
phrase. In other words, how would the world be affected
if we humans stopped guiding and controlling all
microbes and tried to continue our communal way of
living.''

Perhaps the first thing to be affected throughout the
civihzed world, at least during the warm weather, would
be the transportation of milk. For milk, our most im-
portant single food, the food for babes, for the sick,
for the old and young alike, is also a very good food for

52 WHO S WHO AMONG THE MICROBES

germs. So if man does not cool it soon after it is taken
from the cow, to keep down the number of germs pres-
ent— and there are always some, however carefully the
milk is collected — the germs would grow rapidly and
the milk would soon be spoiled or at least become dis-
agreeable as food for humans.

Moreover, if the milk had not been extraordinarily
guarded in its collection and in the choice of the cows,
or if it had not been pasteurized, disease-producing
germs that might be present could increase to danger-
ous numbers.

We would have to go back to the old practice still
in vogue in some parts of the warmer countries, as in
sections of Cuba or Spain — that of having a goat taken
about from house to house and milked at the doorstep ;
or, as in earHer days in many parts of the world, that of
taking our bottle or pail to the cow's stable so the milk
could be obtained and used fresh. Or we might allow
milk to become naturally soured, as they do among
nomadic tribes or in some tropical countries where they
cannot get ice. Of course, they take unconscious ad-
vantage of microbal activity in allowing the bacteria to
grow and produce the acid that sours the milk quickly
and so interferes with the action of the putrefactive
bacteria.

All the products associated with milk as a commercial
industr}^ — cream, butter, cheese — would be affected, at
least in production on a large scale, where microbes are
used for starters, flavors and colors. In short, the dairy
business would be practically wiped out. If man stopped
his control of germs, even the wholesale manufacture
of desiccated milk and completely dried foods in gen-
eral, which are prepared to control microbal growth,

HOW NATURE REACTS TO MICROBES 53

would also cease, though this method was used at first
by individuals not knowing of its effect on microbes.
Other industries depending upon refrigeration, such as
cold-storage plants, and so on, would also be elim-
inated.

Then industries growing out of the use of high tem-
peratures for killing microbes or stopping their growth
would cease. Pasteurization of milk has already been
mentioned. The whole canning industry, including the
making of condensed milk, would be shut down.

Business depending upon the conscious use of
microbes for aiding in certain processes, such as the
tanning of leather, the retting of flax, the production
of ensilage, the production of alcohol through yeast,
the making of bread with j-easts, and many other in-
dustries— all of these would disappear as industries on
a large scale. Even if the making of wines and beers did
continue for a while, their products would become un-
desirable or, as Pasteur said, "sick," through their
being contaminated with microbes that develop dis-
agreeable tastes and smells, or w4th microbes that inter-
fere with the gro^\i;h of the j'easts and produce products
hke lactic acid instead of alcohol.

Food poisoning, with its tragic spectacular effects,
would increase.

Fruit and vegetable growing on a scale large enough
to meet the needs of great masses of people would
gradually cease — first, because of bhghts due to the
lack of spraying, and second, because of soil depletion
from intensive cultivation. Of course, barring these two
hindrances, the life cycle of plants and animals would
go on, but agriculture as an industry would cease.

Animal raising on a large scale hkewise would be

54 WHO S WHO AMONG THE MICROBES

greatly interfered with, due to uncontrolled epidemics,
the lack of the right kind of fodder and the proper care
of waste products.

Last would occur the disappearance of large com-
munities of civilized man through disease and starva-
tion. The human beings that might survive would be
forced back to a nomadic life, taking nature as they
found her, moving with game and away from soil de-
pletion and spoilage, eating meat even then preserved
by natural freezing or drying, eating maggots or ants
as titbits. Thus a proportion of survivors might exist
for a "natural" span, as did early tribes and as do the
nomads of to-day, such as the most northern Eskimos,
who move from place to place as their sources of food
supply change.

Whatever care nature takes of these tribes is done
without their understanding how or why. They only
know that they are constantly facing disease and star-
vation if they do not move to new quarters where game
and soil are good.

Those who earlier decided that they wanted to live
in larger groups in settled homes found that in order
to do so their food and water had to be brought to them
freed from harmful microbes, and that their waste
excreta had to be taken away by watercourses where
dilution, sedimentation and oxidation would lessen their
menace; or they had to be otherwise made innocuous
by such means as filters or chemicals. And so our towns
and cities with their sanitary codes grew.

Even if man should exercise partial control over
microbes — that is, if he should ice or sterihze his foods
when necessary for their preservation, dispose of his
waste products or sewage in an ordinarily hygienic

HOW NATURE REACTS TO MICROBES 55

manner, spray his fruits and vegetables sufficiently, see
to it that his soil has the proper nitrogen-fixing bac-
teria and other essentials for the cycle of life, even then
he still would have to contend with the pathogenic
germs that hve in or on himself and other animals.

How would these act if man did not try to control
them and employ them? Does it look, to use the figura-
tive language of our sentimental naturalists, as if
"nature wants man or the microbe to survive"? The
story of the black death, of the fight against yellow
fever and pernicious malaria in the building of the
Panama Canal, of the typhoid fever and cholera tolls
in India and other parts of the world, of the great
influenza pandemics, must point these misguided ones
toward the view that the microbe is, at least sometimes,
a favorite of Dame Nature, who, if not interfered with
by that "unnatural product" man, will assist the
microbe in unknown ways to develop and strengthen
its toxic powers and other weapons of offense against
man.

"But," these people cry, "some people recover spon-
taneously from disease due to epidemic microbes and
other poison-producing germs, even after the most
severe attacks, so nature must sometimes assist man
too. How does she do this ?" "It is true," the thoughtful
ones answered the first questioners, "and we may be able
to find out why some animals recover from disease and
some die, if we do more studying." So they kept on
tliinking, observing, questioning and experimenting.

It was early noted that people and other animals who
recovered from certain diseases seldom or never had
another attack, and that when they recovered from
certain other diseases they seemed to get another attack

56 WHO S WHO AMONG THE MICROBES

as readily. Why? How? continued to ask the few. The
attempts to answer these puzzhng whys and hows con-
stitute the history of our knowledge of the controlled
prevention and cure of the infectious diseases. Bit by
bit these searchers learned something of how nature
attempts to protect man against the inroads of the few
but very dangerous pathogenic microbes, and how man
can improve these methods. We learned that nature's
methods are incomplete and haphazard. We learned
that man, guiding, assisting and controlling nature in
these haphazard methods, is able, with the knowledge
gained from his investigations, to devise clean, con-
trolled and intensified improvements of these methods
that are many times more effective in the prevention
and cure of certain diseases than are the slow uncertain
methods of unassisted nature, with her tragic epidemics.

To illustrate one of the ways developed by man for
improving nature's methods — in other words, to show
how he must be considered as a part of nature in the
broader sense — we will give a brief sketch, first, of how
nature unaided by man takes care of a child who be-
comes infected with a toxic diphtheria bacillus, and
second, how man has aided to make this care better.

The child gets these germs into its throat, at school
or elsewhere, usually from a playmate, who either may
be just beginning to have diphtheria or may be only a
healthy carrier of the germ. The bacilli may be trans-
mitted either directly through the sputum (spit) by
the sputtering of the germ carrier in talking, coughing
or sneezing (droplet infection), or by kissing, or by
other contact such as infected hands, hands that so
often go into the mouth or nose of even the best brought
up child; or the bacilli may be carried indirectly

HOW NATURE REACTS TO MICROBES 57

through using a pencil or other article the carrier has
had in her mouth, or through tasting a bit of her
sandwich or other food, or even having a chew of her
gum.

In the "good old days" of nature's methods unaided
by man it was not known that there was such a thing
as a health}^ human carrier of dangerous microbes —
that is, a person who is either naturalh' immune or has
developed immunity- through having had an attack of
the disease, or through vaccination (acquired immun-
ity) ; nor was it known that germs are conveyed by
infected droplets of sputum expelled through the ex-
plosive talking of the carrier.

People thought in those days that the air continued
to contain these ^^cious germs indefiniteU", and they
devised elaborate methods for fumigating the air after
a patient had recovered from a contagious disease. A
large part of the force of public health departments
was made up of fumigators, and a considerable labora-
tor}' force was employed to carry out the tests thought
necessary to show that the fumigation had been
thorough.

But after carriers were discovered and the chief
source of new cases of infectious diseases understood, it
was learned that such elaborate fumigation methods
were usually unnecessary. It is true that the fine spray
from the mouth in coughing or explosive talking or
from, the nose in sneezing may often reach far, but
these microbe-containing droplets do not stay sus-
pended in the air. They fall upon any near surfaces
and, as they dry, the vast majority of the poisonous
ones quickly die. Of course, when careless people crowd
together, as in meeting-houses of any kind or in buses.

58 WHO S WHO AMONG THE MICROBES

trains or trolleys, danger through droplet infection is
great.

In the fumigation period, not only did they know
nothing about healthy carriers, but they knew no way
of showing, on the one hand, that one child was sus-
ceptible to diphtheria — that is, that it had no power to
resist the inroads of the microbes — and, on the other
hand, that another child was. not susceptible ; that is,
that even if it took in the diphtheria bacilh, it would
not come down with diphtheria.

Now with the aid of a special test we are able to
show which children are susceptible to diphtheria and
which are not. This test, which is called the Schick test,
so named after the one who first demonstrated its use,
will be described later.

If the child is very susceptible the bacilli, once get-
ting into its throat, will grow there and produce that
very strong toxin (exotoxin) that we described in
Chapter III. The toxin will pass through the whole
body of the child, causing a very severe attack of
diphtheria, and the child may die. If he recovers, it
means that his tissues had the power to respond to the
attack of the bacillus and its toxin by manufacturing
counter-toxins or antibodies that neutralize the effect
of the bacillus. If he only made just enough antibodies
to combat that attack, he might be left with very little
or no power of resistance against another attack. Such
children, if left to nature, might have two or more at-
tacks. If man did his part in the workings of nature he
would make the Schick test on a child and would be able
to judge from that whether that child could be assisted
in the production of diphtheria antibody (antitoxin)
by giving several doses of diphtheria vaccine. You will

HOW NATURE REACTS TO MICROBES 59

learn later that this has been done successfully on a very
large scale, first among the children of New York City
and then throughout America and other parts of the
world.

If a child has a little power to resist the diphtheria
bacillus he may have a lighter attack of diphtheria,
because his tissues respond more readily to the attack
of the bacillus, producing more antitoxin. After he
recovers he usually has a greater immunity, which may
last indefinitely, and he may never get another attack
of diphtheria. Of course, such children respond very
readily to the vaccine and remain immune probably
forever after once being vaccinated.

The reaction of the human host in successfully com-
bating infection by the diphtheria bacillus illustrates
the way in which one kind of antibody is produced and
how it acts. That is, the body cells of the host manu-
facture an antitoxin that neutralizes the soluble toxin
(exotoxin) formed by the bacteria.

Certain microbes, as we have said in the preceding
chapter, manufacture another kind of toxin, the so-
called endotoxin, which is not given out freely from
the microbe cell body in their growth, as is the diph-
theria bacillus exotoxin. It is supposed to stay in the
cell body until the microbe breaks up in death; or the
pathogenic action of certain forms may be the result
of toxin formed in the extraction of host cell substance
while the organisms are growing there.

At any rate, the antibodies stimulated in the host by
this type of poison are more complex than those stimu-
lated by the exotoxins. They cannot neutraHze the
harmful action of these microbes without the help of
another substance that is normally present in the blood.

60 WHO S WHO AMONG THE MICROBES

This substance is called complement because it aids
the antibody. When a pathogenic microbe of this type
attempts to invade an immune animal, this complement
cannot act until the specific immune body, or antibody,
attaches itself to the germ ; then the complement unites
with the immune body — in technical terms, becomes
fixed to it and helps dissolve the germ membrane, re-
leasing and making innocuous the cell contents and kill-
ing the germ. Neither antibody nor complement can
act alone.

Tliis kind of specific antibody may be greatly in-
creased in a person or animal by repeated doses of the
specific vaccine. The serum also of animals that have
received many doses of the vaccine may have some effect
in curing certain infections, but the practical effect is
not so marked as is that with antitoxin serums. These
serums are called antimicrobal or germicidal or lytic
serums. They are called lytic because they dissolve the
cells that were used to stimulate their production. Not
only microbal cells but other animal and plant cells may
stimulate the production of a similar serum. Each
serum is specific ; that is, it reacts only on the cells that
were used to stimulate its production.

This fact is made use of in the employment of a well-
known test called the complement fixation test, one form
of wliich is the very famous Wassermann test.

Both of these tests are used chiefly in helping to
detect infections caused by special types of micro-
organisms.

The Wassermann test is used to detect syphihtic in-
fections. There is no need to add that this test is in
frequent demand. A considerable part of the labora-
tory force in most of our so-called diagnostic labora-

HOW XATUEE REACTS TO MICROBES

tories is employed in carrying out this test. It is a very
complex one and needs expert technicians to carry it
out in a satisfactory manner.

Another important diagnostic test is made with
serums stimulated by the injection of specific microbes.
This is called the agglutination test. Serum from im-
mune animals contains a substance called agglutinin,
which, when the serum is added in appropriate dilutions

(a) Microscopic field, showing
the top of a hancing drop in
a normal culture of typhoid

BACILLI.

(b) Microscopic field, showing
a cross-section of the drop in

(A).

to a suspension of the microbe used to stimulate it,
causes these microbes to gather together in little clumps
or to agglutinate. This is the most specific test we have.
Only the microbe used to stimulate the serum that
agglutinates it, or a like microbe from any source, will
be specifically agglutinated by this serum. This test
has been proved to be practicable in detecting infections
due to the typhoid bacillus and to a number of other
microbes. As applied to the typhoid bacillus, it is known
as the Widal test, so named after the one who first
apphed it practically.

WHOS WHO AMONG THE MICROBES

In its entirety this test is also a very complex one.
It is then called the absorption of agglutinins test. It
is this complete test we mean when we say a microbe
is specifically agglutinated. It is considered the ulti-
mate test for determining the identity of microbes from
different sources that look alike. For each microbe when
added to its specific serum in sufficient numbers will
absorb all of its specific agglutinins and none of those

F!g. 8
(c) Microscopic field, showing

THE TOP OF A DROP WITH THE TT-
PHOID CLOMPED OR AGGLUTINATED.

(d) Microscopic field, showing

CliOSS-SECTION OF THE DROP IN

(c).

stimulated by the injections of any unrelated microbe.
So, if we put a sufficient number of a microbe whose
identity we are not sure about into a serum that we
know, by previous tests, contains the specific agglutin-
ating substance for a known organism of the same
appearance, and let it stand the required time at the
right temperature, we get the serum free from the un-
identified microbe by centrifuging, and put into it a
suspension of the known organism; then, if the un-
identified organism is the same kind of a germ as the
known one, it will have absorbed all of the agglutinins

HOW NATURE REACTS TO MICROBES 63

of the known organism that were in the serum and
there will be no agglutination of the known organism,
as there was before the unidentified organism had been
allowed to remove the agglutinin. This is a very useful
test to help determine the relationship of strains in an
epidemic.

There is still another way known by which animals
combat dangerous microbes. This is the most spectacu-
lar way of all and the one first discovered. We didn't
describe it first, however, because the mechanism of its
action is more complex than that of any other protec-
tive mechanism.

Circulating in the blood of all of us higher and lower
animals are certain ameboid cells called white blood
cells or leucocji;es. These possess the power, under
certain conditions, of seizing and drawing into their
bodies certain of the microbes that have passed our
first set of barriers, skin and mucous membranes, and
gotten inside of our tissues.

The important part played by these wandering
white blood cells in destropng certain microbes was
first surmised by the Russian Metchnikoff while study-'
ing the digestive processes of the larvae of starfish. He
saw through his lens certain freely moving cells take up
some colored pigment he had injected into the larvae.
He thought "if such cells can take up foreign matter,
they can probably take up microbes too. And perhaps
all animals are protected from disease germs in this
way."

After many trials and exciting demonstrations he
was able to convince other investigators that this kind
of cell actually devoured some germs.

But at first his assumption was too inclusive. He be-

64 WHO S WHO AMONG THE MICROBES

lieved that all harmful microbes were combated in this
way and that this was the only w^ay animals have of
guarding against disease. And long and hot was the
fight among investigators to prove that tliis destruction
by phagocytes or cell destroyers, as Metchnikoff called
them, was only one of the weapons animals have
evolved to protect themselves against their germ foes.

Some investigators, as usual, went to the other ex-
tremes and thought that these phagocytes were only
scavengers, taking up any foreign particles without
selective action. But soon there were a host of research
workers, chief among them Bordet, Wright and Neu-
feld, who showed that there is a certain substance
circulating in the blood that attaches itself to the
microbes, making it more easy for them to be engulfed
and destroyed by the phagocytes. It seems to prepare
the germ for being devoured. For this reason Wright
gave this substance the name opsonin, from the Greek,
meaning, "I prepare for."

An opsonin for a given microbe may become in-
creased in amount in the blood of an animal that is
recovering from an attack by the microbe, or that has
been given regulated doses of a vaccine made of the
microbe.

The resulting increase in the defensive power of the
leucocytes is not as lasting as is the immunity pro-
duced against the other poisons of the microbes.

The question of why and how certain microbes, as
well as other foreign substances, do not cause a decrease
in the susceptibihty of those who have been invaded by
them or their products is one requiring so much techni-
cal knowledge to comprehend the little we know about

HOW NATURE REACTS TO MICROBES 65

it that one can only say, as one has to say so often, we
must leave it to the special investigators.

In these fragmentary sketches of how human
beings and other higher animals react to attacks by
harmful microbes, how a balance is reached between
man and microbe, we have attempted to show that our
body cells, on the whole, respond to the different poisons
and other microbal products by manufacturing sub-
stances that neutrahze these poisons and other products.
These neutralizing substances are called antibodies ; the
poisons and other products stimulating the production
of antibodies are called antigens.

Antigens of harmful germs that are injected into
animals for the express purpose of stimulating the pro-
duction of antibodies that may help cure or prevent
disease are called vaccines, because they are used for
the same purpose as was the first vaccine made from
coTvpox virus.

The chief reason why more people in these days are
not impressed with possible dangers from pathogenic
germs, why so many say "What is the use of vaccinat-
ing?" is that they forget that many people are immune
to certain diseases because of the "wdde-spread vaccina-
tion that has been going on for years.

If we should stop the use of all vaccines and serums
now* how much could we do to prevent infectious dis-
eases by other hygienic methods alone? We can answer
that if such hygienic methods were strictly carried out,
most infectious diseases would be prevented. Why,
then, you may ask, are not such measures emploj'ed?
We answer, because it is a practical impossibihty to
carry out all of these measures.

66 WHOS WHO AMONG THE MICROBES

Let us consider this. We know that microbes that are
pathogenic for human beings may be conveyed through
human or lower animal carriers, who may be normal,
diseased or convalescent ; we know that the germs may
pass to another, directly, through fine droplets of
sputum spluttered out from the mouth in talking or
coughing, or from the nose in sneezing, or through
the hands or other parts of the body contaminated
with or containing the infectious germs ; or they may
pass indirectly by any utensils coming in contact with
these infectious parts of the carrier. Food handlers in
the picking, packing and transportation industries,
jobber, fruit-stall and other human agencies contribute
to the bacterial content. Then there are the dust and
filth from flies and other vermin and lower animals.
To prevent infection from such carriers means that all
human beings must wear masks, that their hands and
their excreta must be thoroughly steriHzed; it means
that in insect-borne diseases the insect carriers — mos-
quitos, flies, fleas, ticks — must be destroyed; it means
that in diseases carried by other animals, Hke rabies
transmitted by stray dogs, these animals must be
destroj^ed.

One can reahze after a moment's thought how im-
practicable— nay, impossible — it would be to carry out
measures that would absolutely rid us of all sources of
infection. The whole question of the use of hygienic
measures, including the so-called sanitary procedures,
is one of adjusting the measures needed to destroy all
dangerous germs to the measures that can be practi-
cally apphed.

There is no question but that many procedures that
are practicable result at least in lesbcning the number

now NATURE REACTS TO MICROBES 67

of dangerous microbes ; and this is a worth-while thing
to do, since the number of microbes is of importance in
determining infection in many individuals. Those that
have at least a httle resisting power can take care of a
few pathogenic germs.

Even if we could rid all carriers and their surround-
ings of all pathogenic germs, at a special time in a
special neighborhood, would it be desirable ? How would
nature respond to this state of things.'^ Antibodies would
cease to be formed in these people. The people, or at
any rate their descendants, might become fully sus-
ceptible to disease germs. If they went to another part
of the world where such microbes still existed or if a
carrier visited them they could be easily attacked.

There was a tragic illustration of this in the World
War when troops came in from country places where
they had not been exposed to measles. Epidemics of
measles broke out in the various camps, attacking
chiefly these country boys. They developed the disease
in very severe form and many contracted a complicat-
ing pneumonia, resulting in a high mortality. We have
had other striking examples in the American Indians
and Eskimos when they have come in contact with
diseases new to them, brought to them by people from
the civihzed world. Many have quickly succumbed to
these diseases.

These tragic incidents show us that If we cannot have
complete hygienic protective measures, and if we have
no vaccines, we are bound to have more or less wide-
spread fatal epidemics of certain diseases that we now
prevent by vaccines. Notable among these are small-
pox, diphtheria and typhoid fever.

We still have epidemics of influenza, measles, infan-

<J8 WHO S WHO AMONG THE MICROBES

tile paralysis, whooping-cough, pneumonia and so on,
chiefly because we have no efficient way of vaccinating
against them or of otherwdse preventing them. We
either do not know the organism that causes them, or
it is impossible to make or we have not yet learned how
to make an efficient vaccine.

We see, then, that it is up to man to do everything
he can to better all natural processes that promise to
help him preserve and improve his life, to take his part
in "nature's plan."

CHAPTER V
FAMILY RELATIONSHIPS OF MICROBES

As determined by human beings who know little about them,
hence constant regrouping — "Family tree,"

After all, from the human standpoint, we repeat there
are only a comparatively few species among the
microbes that are known to have a potent power for
good or for evil upon man's life.

Where are these important ones placed in the three
great classes described in the second chapter? How
closelj" are they related? What traits have they in
common? Have they any "poor relations" who may
need to be considered? These are some of the ques-
tions we are now going to try to answer.

If we follow, as well as we are able, considering the
minuteness of these creatures, the biologists' rule of
grouping together, first, those that have similar forms
and morphologic structure, drawing only a httle on
their physiologic activities, we find that these more
important microbes fall into different groups or fam-
ilies among the great classes.

Students of biology know that the term "family" is
used by classifiers to indicate a group of individuals
that possess more traits in common than those classed
as a tribe and less than those classed as an order. The
word "order" is the name given to the first division
under the broad di^^sion labeled class. The term "tribe"

70 .WHOS WHO AMONG THE MICROBES

indicates a group having more points in common than
the group called genus (plural genera). Finally, the
term "species" is used for the individuals making up
the genera. We may give as an example the position
of a well-known bacterium: Class — Bacteria or schiz-
omycetes. Order — Eubacteriales. Family — Coccaceae.
Tribe — Streptococceae. Genus — Streptococcus. Species
— Streptococcus pyogenes.

Of course, as commonly used the import of the words
"family" and "tribe" follows the custom of being quite
different from what they had at their traced origin,
so they have come to possess a number of different
meanings ; hence, qualifying words or introductory ex-
planations must often be added to indicate what they
may signify. For example, the human family, the mid-
European family, the tribe of Judah, and so on. As
applied to human beings to-day the term "family" may
mean race, the term "tribe" kindred and the term genus
family. Among botanists and zoologists the terms
family and tribe as used by the one group of scientists
denote ranks slightly different from those used by the
other, and the terminations used to designate these
terms are different respectively.

Among the bacteria or lowest plants there are nine
families. Among the molds or next higher plants there
have been so many families described that we shall con-
sider them here as the four groups that have commonly
been recognized. Among the protozoa or lowest animals
we shall describe hkewise four large groups.

Some of these families seem to be closely related be-
cause of similar traits, though the individuals may not
appear ahke in shape and structure, and some indi-
viduals that look ahke may exhibit such different traits

FAMILY KELATIONSHIPS OF MICROBES 71

that they are placed at least in a different tribe or
genus.

Then there are those mysterious invisible or ultra-
microscopic viruses, in which we cannot yet distinguish
individual forms, that can only be differentiated by
certain physical and biochemical properties. They must
still be studied as a group, though some of them may
not be closely related in structure.

Of course, these groups are being actively studied
by investigators throughout the world, and new facts
and new relationships are being brought to light which
may lead to some rearranging and renaming of the
families, tribes and genera and of individuals in them.
This has already happened a number of times. In fact,
several changes have been made since we began writing
this book. So the grouping or classification of these
minute organisms is still in the depths of dispute.

To know just where to place each variety so that it
falls into a significant group is often an impossibility
with the amount of knowledge we possess. Even to do
what little we are able with the aids we have requires
so much painstaking study that few have had enough
time or other means to carry on the required investi-
gations. We are therefore still far from a satisfactory
grouping of the individuals from the standpoint of the
systematic biologist. As we have said, in order to show
the relationships of these individuals so that they may
be given a specific name and these species grouped as
genera, we have had to draw largely upon physiologic
and biochemical characteristics, since in such minute
beings structural changes if they do accompany bio-
chemical cannot readily be demonstrated.

Among other comphcations that make the grouping

72 WHO S WHO AMONG THE MICROBES

of these minute organisms difficult or uncertain is the
possibility — nay, the certainty in a number of forms,
if not in all — of their changing traits that may have
been used as a basis of grouping; that is, the progeny
of certain families, while they may not change in visible
form, may act differently under similar conditions be-
cause they have either lost old traits or taken on new
ones. They usually lose quahties rather than acquire
new ones. These fairly rapid changes take place in a
comparatively short period of time from our stand-
point, but one which allows thousands of generations
of the microbe, which may pass through as many as
thirty generations in a day.

The changed actions may be of extreme importance
to man. Thus toxic bacteria may become non-toxic,
virulent ones non-virulent, and many lose or change
substances and characteristics that were of value in
identifying them as well as of grouping them. Investi-
gators have devised ingenious ways for studying these
changing organisms.

In the first place, the students must be as sure as they
can be that they are starting out with a pure culture
from a biologic standpoint. So they begin by trying
to isolate a single organism that they can see under
the microscope. The ordinary way of getting some-
thing that is called a pure culture, the way by colony
fishing that we described in the second chapter, is not
considered accurate enough by these fishers of germs.
But with all their care, and though the method they
use — the capillary tube method, as it is called — is theo-
retically supposed to be the best method of getting a
pure culture, it does not rule out dingers among the
germs too small to be seen with our best magnification.

FAMILY EELATIONSHIPS OF MICROBES 7S

However, the chances are that they get a pure culture.
At any rate they call it pure. And the earlier workers
thought that under these conditions they had obtained
a microbe upon which they could base predictions of
future activity.

But alas ! for their expectations. It was soon found
that even these cultures, as we have said, do not always
remain the same as they were when the}'^ were originally
isolated. They split into those which develop colonies
that are coarse or fine, rough or smooth, spreading or
compact, mucoid or dry, and that have still other
characteristics that are different from each other. Some
lose or increase their toxicity or virulence, some lose
their power to ferment certain sugars, some lose their
power to agglutinate and to produce or absorb agglu-
tinins. This last, as we have pointed out, is considered
a very important method of species differentiation, and
the most important if not the only test for determining
epidemic strains.

All of these changes have been comparatively little
studied yet, so we are still in a state of indecision as
to their exact importance in classification and in other
relationships in general.

We only know that they are making us more careful
than ever in drawing deductions from observations
carried on for short periods of time and wdth insufficient
controls.

We see, then, that the so-called specific names of
these organisms are liable to change and are therefore
not so important to remember. Of course, they are of
interest and importance to the biologist — as an aid in
his studies, and to all of us as convenient if only tem-
porary handles.

74 WHO S WHO AMONG THE MICROBES

The family or group names are less liable to change
and their common names are quite easy to remember.
In this chapter we will list the family or group names,
giving first the common names and then the specific
names in parentheses following them.

The famiHes among the bacteria that we are going
to discuss are:

The coccus or berry-shaped family (Coccaceae).

The nitrogen-using family (Nitrobacteriaceae).

The family of bacilli without spores or the non-spore-
bearing family (Bacteriacese).

The family of bacilli with spores or the spore-bearing
family (Bacillaceae).

The comma family (Spirillacese).

The coiled-hair family (Spirochseteceae).

The false-branching family (Mycobacteriaceag).

The true-branching family (Actinomycetacese).

The four groups among the yeasts and molds are :

The budding fungi or yeasts (Blastomyceteceas).
The non-sepurate molds (Phycomyceteae).
The septate molds (Mycomyceteceae).
The imperfect molds (Fungi imperfecti).

The four groups or classes among the protozoa are :

The flagellates or forms moving by few hairs (Masti-
gophora).

The amoebas or forms moving by pseudopods (Rhizop-
oda).

The seed or spore-forming parasites (Sporozoa).

The ciliates or forms moving by many hairs (In-
fusoria).

Many of these families have grown so large that they
have been separated into sub-famihes or tribes. Thus,

fa:viily relationships of microbes 75

the coccus family has three tribes, known as Neissereae,
Streptococceae and Micrococceae. The nitrogen-using
bacteria have two tribes, Nitrobacteriaceae, or bacteria
oxidizing nitrogen, and other simple elements, and
Azotobacteria, or nitrogen-fixing tribe.

The famil}' Bacteriaceas is very large; it has eleven
tribes, Onh' five of these are kno^vn to be of marked
importance to man. One of the other tribes is of in-
direct importance, since it contains man}' members that
are very pathogenic for plants ; for example, the bhght
of pears and apples, the soft rots and black and yellow
rots of melons, potatoes and beets, the blights of a host
of other fruits and vegetables, the leaf spots in tobacco
and other plants, and so on, are all caused by members
of this bad tribe, called Erwinias. Many of the other
tribes, too, are of great indirect importance, because
they are soil bacteria that help in the great work of
breaking down the organic material of dead plants and
animals into the simple components that can be used
again by hving plants.

In one of the less directly important tribes is the
historical bacillus that used to be called Bacillus prodi-
giosus ; but now classifiers have decided that its right
name is Serratia marcescens. This produces a blood
red pigment, and was used earlier by some to deceive
the superstitious in regard to what these deceivers
claimed was a miraculous appearance of blood. It may
produce red spots hke drops of blood on stale moist
bread, on boiled potato or on any moist organic matter.
It may cause milk to become red, and may break up
fat and cause rancidity of butter, but it is not poisonous
for man. This bacillus, because of its small size and
conspicuous growth, is often employed to detect de-

76 WHO S WHO AMONG THE MICROBES

fects in the fine stone and porcelain filters that are
used so frequently in the study of microbes.

Another bacillus in the same tribe is a very minute
one that is found sometimes in the pus of abscesses and
other purulent conditions. It produces a blue-green
pigment with a pungent scent. Because of its easy de-
tection by the color, it is also used in certain tests
such as determining the efficiency of room disinfection.
It used to be called Bacillus pyocyaneus, but now it
is known among the purists as Pseudomonas aeruginosa.
It is only slightly pathogenic for man. This whole
tribe is composed of individuals that produce beautiful
pigments, red, yellow, violet, green, blue.

Now we come to the two tribes of this big family
that are of greatest influence in man's life. The first
two of these might be called the alimentary canal
tribes, because they are found chiefly in this impor-
tant part of man's body, some only in health, some
only in disease, some in both health and disease. They
are called Bacterieae and Lactobacillieae. In one of the
other three tribes (Pasteurelleae) is the famous Bacillus
pestis, the cause of more fearful epidemics, spectacu-
larly recounted in history and literature, than are the
ravages of any other microbe. Of the two remaining
tribes, in one, the blood loving tribe (Hemophileas) are
the misleading influenza bacillus and the irritating
pertussis bacillus (whooping-cough bacillus) ; in the
other is an encapsulated bacillus found quite frequently
in colds. Whether it has much to do with them is an-
other question.

The next family is composed of spore-bearing bacilli.
It has two branches, and one is a big branch of aerobes
or germs that grow in the presence of oxygen. Only

FAMILY RELATIONSHIPS OF MICROBES 77

one of these is pathogenic for man, but this can be
very dangerous, causing mahgnant pustule, septicemia
and death. It is called Bacillus anthracis. The others
of this branch are soil bacteria that help in decomposi-
tion. The second branch is composed of those that can-
not grow in the presence of free oxygen; that is, they
are anaerobes. Here we have a number of marked dis-
turbers of man's peace. The lockjaw bacillus; the
botulinus bacillus, that most famous of the food-pois-
oning bacteria ; and a number of wound bacilli, causing
infection of wounds with the development of gas in the
tissues, followed by gangrene, are all found here.

The curved or comma-shaped, family are chiefly
water bacteria, though some are found in the intestinal
canal. They may either appear as segments of spirals,
the comma forms, or some may remain attached to
each other, forming spirals like corkscrews or wire
springs, when they look something like members of the
next famih\ They are called vibrios or spirilla. Among
these comma forms is only one pathogen, the dreaded
cholera bacillus. Among the corkscrew varieties is one
that all students know, because it is used for demon-
stration purposes. It is called Spirillum rubrum. It pro-
duces a beautiful red pigment in the depths of the
medium.

The next family might be called the coiled-hair
family, since its members were given the name Spiro-
chetes because they look like coils of hair. As we said,
they look something like some spirilla or the family we
have just mentioned. On the other hand, some forms
resemble certain flagellated forms among the protozoa.
So some classifiers have considered them bacteria, others
protozoa. Since the weight of evidence seems to be with

78 who's who among the microbes

the former, we class them for the time being with the
bacteria. To this family belongs the famous and noto-
rious pale spirochete of syphihs, now called Treponema
pallidum.

The next family is the pseudo-branching or false-
branching family. Some authorities are willing to give
its members the benefit of the doubt and place them
among the true branchers, but what are taken for
branches among them are so abortive, and appear only
under such unusual conditions, that it is difficult to de-
cide how to class them. In observing minutely the mode
of growth of these forms the "branches" may be seen
forming after partial division of an organism. At any
rate, the claims put forward for classing them with the
higher bacteria, like many of the claims of aspiring
humans for belonging to the "first families," are not
very strong.

The different groups included in this family by our
latest classifiers are so unHke each other in many re-
spects that each might be considered a tribe, if not a
family, in itself.

Thus, there is the Indian-club-shaped group of which
the diphtheria bacillus, the cause of diphtheria seen
at its worst as membranous croup, is the chief. Then
there is a group the members of which look a little like
the diphtheria bacillus, but they can only grow when
air is excluded ; that is, they are anaerobic. Their effect
on humans is not well understood, but they are supposed
to cause a certain kind of ulcer occurring chiefly in the
mouth. They are implicated also in certain gum
abscesses.

Next there is the acid-fast group, of which that most
insidious and deadly of all germs, the tubercle bacillus,

FAMILY EELATIOXSHIPS OF MICROBES 79

is the chief; and the ungrowable leprosy bacillus is a
near relative.

Last there is the malleus bacillus, the cause of the
glanders or farcy that occurs in lower animals and
occasionally in man.

What a conglomeration of varieties to be placed in
one family ! Can j'ou Avonder that there have to be
changes made, that some have to be moved to other
quarters when we become better acquainted with them?

The next family, the Actinomycetaceae, is composed
of what have been called the true higher bacteria or
the real branching forms. While they are like the bac-
teria in many respects, they are so hke the molds in a
number of particulars that they are classified with
them by some investigators. Castellani in his latest
classification includes among the molds not only these
so-called higher bacteria but even those we have de-
scribed under the common name, false-branching forms.

When we begin to consider describing in a book
of this size the second great class of microbes, the
molds, we are overwhelmed by the number of families
and members of these families that have been reported,
and the much and the little that has been written about
them. A whole branch of biology, called m3^cology, has
developed as a result of the studies of this group.

Because of the many differences of opinion in regard
to their relationships we shall consider as belonging in
this class only those forms that are called by Castellani
and others the true yeasts and molds, and we shall
describe the large commonly accepted groups rather
than the many unsettled families.

First, there is the group called yeasts or yeast-like
fungi. This group includes all those microbes that grow

WHO S WHO AMONG THE MICROBES

usually in the form of comparatively large oval or
spheroidal cells that multiply chiefly by budding. Some

'I LTERABLE Viruses

ll!lKira@MK] @10©OI?3g ©IF LDFE

Hypothetic Tree of Evolution of Microbes

Fig. 9

varieties produce no mycelium or stem-like (thread-
like) forms, except sometimes a few in cultures. Some

O «

— -a

FAMILY KELATIOXSHIPS OF MICROBES 81

varieties form cysts, called asci (meaning bag or sac),
containing usually four spores or a multiple of four.
In others no asci have been seen. The formation of an
ascus has been chosen by classifiers as the chief mor-
phologic trait for separating the yeasts and molds into
two large groups {See "Tree").

These forms were called yeasts, from the Greek word
which means to boil or seethe, because they were first
seen in the foam and sediment of fermenting \\'ines
and beers. A number of varieties now classed in dif-
ferent families by the systemic biologists are commonly
included in this group.

The big group of molds may be called the mycehal
fungi, because the vast majority of them produce
definite long-branching filaments or threads called
mycelium. These filaments are usually much larger than
the threads of the actinomyces, and they often have a
double contour as seen through the microscope. In one
group the filaments have no partitions ; that is, they
are non-segmented, except at certain stages in their
life. This group goes by the name phycomycetes. In
another group the mycelium is always segmented or
septate ; that is, it is made up of chains of cells. These
were called mycomycetes, but now this group is spht
up by the classifiers. The fourth old group called the
imperfect fungi contains all those forms in which a full
Hfe cycle has not been demonstrated. Among these are
most of the forms found pathogenic in man. These too
are now split up.^ In the "Tree" the group proceeding
from the "yeasts without asci" composes the Fungi
imperfecta

^ See table in Castellani's book, "Fungi and Fungous Diseases,"
Am. Med. Assoc, Chicago, 1938.

82 WHO S WHO AMONG THE MICROBES

The last class of microbes we consider, the protozoa,
is also such a large group, and its classification is so
unfinished that we can only describe its common divi-
sion in general terms.

The flagellates have one to several delicate whip-like
appendages wliich help them move about freely. The
majority are harmless water microbes; most of them
have a definite nucleus. Several have a modification of
their body in the form of a fluted membrane attached
by one edge and prolonged as the flagellum. Among
these pecuhar forms called trypanosomes are several
enemies of man and beast.

The amoebae, quoted as the type of man's beginning,
are placed higher than the flagellates by some classi-
fiers. They move about by pseudopods or false feet.
Harmless, free living forms may be found wherever
there are moisture and decaying vegetable matter. The
matured individuals usually contain a single nucleus.
This may divide into two or more, according to the
stage of gro^vth, and the kind of amcEba. Then they
may encyst into resistant forms that may live quiescent
for many years. At least one form is known to be an
active enemy of man.

The sporozoa are all tissue parasites that reproduce
chiefly by forming many spores. That famous enemy,
the malarial parasite, is placed in this group.

The ciliates, those forms that have many delicate
hair-hke appendages over their bodies, are mostly free
living forms found in water. They have the most com-
plex structure of any of the protozoa. With their
double nuclear apparatus and their hairy striations
they present a striking appearance. One only is patho-
genic.

FAMILY RELATIONSHIPS OF MICROBES 83

We have attempted to give some general idea of
distinctive points characterizing the groups and fam-
ihes among the three great classes of microbes.

In the following pages we want to give the family
or group history and the cliief traits of the head or
most important members of each family, tribe or group,
and of those relatives that are considered worthy of
being put in our blue book of microbes.

The question of the historic relationships of these
groups of microbes, of their real origin, of their very
beginning, is still unsolved. We call bacteria the lowest
forms of life, but we do not know whether the other
two classes sprang from them or whether these had
a separate origin, or whether they all had their be-
ginning in a form alhed to one of the filterable viruses,
or — we might keep on adding "ors" for some time
without getting a clue to this so far impenetrable
mystery.

An idea, right or WTong, may be obtained of the
relationship between the different families and a parent
stem, where the new type appeared and the "fixed
types" remained, by glancing at the "tree" on page 80.

Of course, such a "tree" can only indicate the
branches important to man, and like all attempts at
graphic illustration it can only give a rough idea of
possible relationships. Like all trees, pruning and
grafting maj' help it grow more perfectly, or it may
have to be chopped down.

The terminal Hnes indicate genera, and divisions be-
tween these and the main stem indicate tribes and
famihes.

CHAPTER VI
THE COCCUS FAlvnLY

(Coccaceje)

Pus producers — Blood invaders — Lung attackers — Brain
membrane inflamers — Cheese makers.

The coccus family is one of the first three famihes
recognized by the society of bacteriologists. Several of
its members were accepted as being worthy of note be-
tween 1869 (Helher) and 1879 (Pasteur). Even be-
fore this, minute globular forms, which were later iden-
tified as cocci, were seen by that keen-eyed observer
Klebs, and after him by others in wound infections,
though the final proof of their relationship to wound
abscesses was not made until many years later. Because
of their relationship to the formation of abscesses, boils
and purulent lesions generally, the pathogenic members
of this family have been called the pus-forming or pyo-
genic cocci. As they have become better known they
have proved themselves to be a very important family
and should be ranked high among the famihes of bac-
teria— ^high from the standpoint of their effects on
man, but low from the standpoint of morphology.

It is only placed lowest by some classifiers in the
grouping or classification of the bacteria because of
its form — a coccus or berry shape. This spherical form
is accepted by these classifiers as lowest, since it is
assumed to be the simplest morphologic type.

THE COCCUS FAMILY 85

From the standpoint of complexity of acti\'ities
many of its members outrank most of the microbe
world. So manj'-sided are the characters of some, so
sudden and capricious their actions, harmless at times,
harmful at others, that they might be called danger-
ously mischievous. When harmful they may attack al-
most any tissue in the body, but some have a way of
becoming accustomed to a single tissue. Thus, some
forms attack chiefly the skin, others the nerve tissue,
others the mucous membrane of the throat, and so on.

They accomplish their purpose of injuring the tissue
chiefly by penetrating and gro^nng in it and breaking
up its protoplasm by the activity of its ferments. Those
germs that are killed by the body defenses are supposed
to release a toxin as their dead bodies break up, a so-
called endotoxin wliich, if it does not overwhelm the
tissues, causes them to react and produce a complex
antibody like one of those described in Chapter IV.
Only recently it has been shown that some of the mem-
bers form an exotoxin that acts chiefly on the skin and
mucous membranes. Some make a poison that acts on
the Avliite blood cells or leucocytes. Some poison and
destroy the red blood cells, producing the so-called
laking of the blood through the dissoMng or lysis of
these cells, the hemolysis we mentioned in Chapter III.
They have grown into such a large flourishing family
that, as we have said, three tribes have been formed.
Some members of each tribe have forced themselves
particularly upon the notice of human beings because
of their ubiquity and their irregularly harmful acti^'ity.

The first tribe, called micrococcese, is composed of
rounded forms gro^^'ing singly or in pairs, groups or
packets ; it contains many non-pathogenic members

86 WHO S WHO AMONG THE MICROBES

found in air and water. A few of its forms are harmful
and harmless parasites in man. Most of them, as to
staining, are Gram-positive.

The first member isolated in pure culture was ob-
tained from a wound abscess by Rosenbach in 1883.
It grows frequently in clumps like bunches of grapes,
hence its name, Staphylococcus. It is the chief of the
tribe.

Some of the progeny of this coccus develop a beau-
tiful deep golden or orange pigment in their gro^i:h,
others form a lemon-yellow color and others a pure
white growth. These varieties (species) are called re-
spectively the golden coccus or Staphylococcus aureus,
the lemon-j^ellow coccus or Staphylococcus citreus, and
the white coccus or Staphylococcus albus.

The golden coccus is the variety that is most harmful
to man. Usually it is not at all dangerous. It grows as
a parasite on the skin or on the mucous membranes of
the throat of many healthy people without doing any
harm. But if a wound occurs in the skin or mucous
membrane, or a gland (fat or sweat gland) becomes
plugged, lowering the resistance at that point, this
microbe may start growing there and may cause that
horrid pest, an abscess or boil.

Or if the person's susceptibility is increased for any
reason, such as wrong diet, fatigue, exposure to heat
or cold, and so on, a severe tonsillitis or other mani-
festation classed under the name "cold" may follow,
Tvdth the gro\\i;h of tliis organism becoming at least one
of the factors in causing the whole chnical picture.

If the person in this condition is extremely sus-
ceptible to this microbe, or, in bacteriologic language,
if he has no specific antibodies in his tissues, and if

THE COCCUS FAMILY 87

the microbe itself has developed special powers of grow-
ing in these tissues and poisoning them, as some do,
then the germ may rapidly overwhelm the indi^ddual,
swarming in liis blood stream, heart, lungs and all other
tissues and quickly cause death. In such a case death
is said to be due to blood poisoning or septicemia.

In all these cases the susceptibility of the human
being is the more important factor; that is, this or-
ganism is not often so virulent in itself that it can
cause serious epidemics by attacking several individuals
in quick succession, though it may be fatal to the sus-
ceptible individual.

Among the cocci are two close relatives of the
staphylococcus that might be mentioned here, more for
their distinctive forms than because of their effect on
man.

One grows frequently in fours, hence it is called
tetragenus. It is found occasionally in abscesses accom-
panying the pyogenic cocci. It is frequently present
in tuberculous sputum and has been found as the only
microbe in an occasional case of conjunctivitis. It is
supposed to have only feeble pathogenic powers, and is
usually, if not always, only a secondary invader.

The other, called sarcina, is interesting because it
grows in packets of eight or more cocci. It has been
accused of doing a little harm to man, but the case
against it has been dismissed through lack of evidence.

The next tribe to be recognized in this family has
members that make a graceful, beautiful appearance
when gro-v^-ing in liquid media, such as nutrient broth to
which a little serum and sugar have been added. Their
coccus forms remain more or less attached to each
other as they grow, so they often present long chains

88 WHOS WHO AMONG THE MICROBES

which are curved and t\Ndsted, hence the name of the
tribe Strepto (which means tT\4sted) and coccus, or
streptococceae. These chains look hke strings of beads,
and, stained by Gram's method, most of them stand out
as Gram-positive blue or red globules, according to the
stain used, on a contrasting background. They are not
so strongly Gram-positive, however, as are the ma-
jority of the staphylococci. The streptococcus is more
fastidious in its food requirements than the staphylo-
coccus, growing more readily, as we have indicated
above, when a little albuminous material and a pinch
of sugar are added to the medium. Most species grow
scarcely at all at room temperature. These need the
body temperature for their best growth, and they like
the human body to grow on.

It is frequently parasitic in human mouths — espe-
cially in the crypts of the tonsils — but it needs less en-
couragement even than the staphylococcus to grow
through the human body and produce injury to its
tissues. Depending upon the susceptibility of the person
and the character of the strain of streptococci, some
strains grow readily in the blood of their hosts, causing
septicemia; some strains grow more readily through
lymph spaces producing lymphangitis; some strains
grow in the cellular tissues and lower layers of the skin,
when they produce a condition called erysipelas, and
so on.

It puts in an appearance in increased numbers so
readily during the course of almost every contagious
disease that it has often been incriminated as being
the chief culprit in the tragedies of most of the infec-
tious diseases, especially of those whose causes we have
not yet found. Thus, smallpox, measles and infantile

THE COCCUS FAMILY 89

paralysis, as well as diphtheria and other diseases
whose causes are now known, have all at various times
been said to be due to streptococci. Scarlet fever, of all
the so-called specific exanthematous diseases laid pri-
marily at the door of the streptococcus, is the only one
in which a streptococcus has been proved to be Its spe-
cific cause.

There are several facts that have led microbe hunters
to accuse streptococci wrongfully of being the cause
of the other diseases. First, the fact that they are so
frequently present in all these other conditions ; second,
the difl^culties our microbes have of establishing alibis
when the deed is actually committed, when the disease
really begins ; and third, most important of all, the
ability of the real destroyers to remain hidden. All this
has made it very difficult to rule out these ubiquitous
pushing microbes as being the real, the specific cause
of the disease.

In some cases, notably In poliomyelitis and measles,
they have not been absolutely ruled out yet. There is
no question but that many varieties of streptococci are
dangerous secondary invaders and often cause death
when the original specific cause of the disease might
not have done so. But we noAv know that they cannot
cause specific diphtheria or smallpox; that they prob-
ably— at least any kno\\Ti forms — do not cause measles
or poliomyelitis, and that certain forms do cause scar-
let fever, erysipelas and puerperal fever.

The history of how these streptococci were finally
proved to be the specific cause of the disease knowTi
clinically as scarlet fever is a record of one of the most
• — shall we say? — exasperating of all searches In pur-
suit of the elusive microbe. Clue after clue was found,

90 WHO S WHO AMONG THE MICROBES

and proof was in sight several times but was not recog-
nized by authorities. Research work of this type is well
described by a remark of Haldane, published in a re-
cent "Atlantic INIonthly," concerning new facts dis-
covered. He said that such discovery was usually based
upon "years of very persistent and rather dull work in
hundreds of laboratories," work that "had occupied
far more time and probably required more thought and
patience than the final stages."

Here is the story of the streptococcus and scarlet
fever.

Almost as soon as streptococci were recognized as a
distinct group among cocci, they were accused of caus-
ing scarlet fever. So many of these little chains of
cocci were found in the throats of scarlet fever patients
that the germ searchers thought these must surely be
the cause of the disease. Then when similar chains
were found in large numbers in many other diseases,
some investigators said "they cannot be the cause."
Others said, "But perhaps the streptococci in scarlet
fever have special traits that we haven't discovered,"
and they proceeded to watch them very closely, and
to try every test on them they could de\ase. And they
pubhshed their discoveries, detailing lengthy experi-
ments to show that they discovered a new trait that
was possessed by the scarlet fever streptococcus alone.

But then along would come another group of re-
search workers, who also published lengthy reports to
show that these first workers had not used enough con-
trols and that their test applied to many streptococci
from sources other than scarlet-fever patients.

Among these numerous tests was one more important
than the others, in that it divided the streptococci into

THE COCCUS FAMILY 91

three large groups. Schottmiiller (1903) found that
certain streptococci produce a poison that destroys red
blood cells by dissohang them completely (laking their
essential hemoglobin), causing the so-called hemolysis
we described in Chapter III. These cocci were called
hemolytic streptococci. He found further that some
streptococci produce a green color and only slight
hemolysis in their growth in blood. These he called
green streptococci. Others were found that produced
no visible change when they grew on blood; these were
called anhemolytic streptococci.

Investigators soon found that it was the hemolytic
streptococci that occurred in such numbers in scarlet
fever. But at the same time this kind was found in
erysipelas, puerperal fever and several other diseases,
so tliis test wouldn't work in separating them.

Then a Viennese physician, Moser, reported that the
serum of horses that had been injected with hemolytic
streptococci from scarlet fever agglutinated only strep-
tococci from scarlet fever and no other streptococci,
and that the patient's blood did the same. And he made
a more important announcement than this. He said that
his horse serum contained a specific antibody that cured
most of his cases of scarlet fever.

Of course, detractors came along. They always do,
especially at the beginning of an investigation. Aronson
and others said that the horses they injected did not
give a serum that had a curative effect, neither did it
regularly agglutinate hemolytic streptococcus strains
from scarlet fever.

Schick, who later devised that famous skin test used
in combating diphtheria, pointed out that the reason
people were getting such irregular results was because

92 WHOS WHO AMONG THE MICROBES

not all horses respond equally to the injection of cocci.
You had to choose your horse. This point we have found
to be true for horses in response to all disease germs.
But at the time not much attention was paid to Schick's
observations.

In the meantime, every one was hunting for a method
of demonstrating a toxin that might be produced by
these hemolytic cocci and might be separated from
them.

Then a Russian, Gabritschewsky (1907), reported
that he could produce scarlet fever in children by a
filtrate of his broth cultures of hemolytic streptococci
from scarlet fever, and that the children after they re-
covered were immune to scarlet fever. A colleague of
his, Savchenko, at the same time, showed that if he
injected the toxic filtrate of his cultures into a horse
and then the whole culture, he could get a serum that
would cure scarlet fever.

But the world outside of Russia and Austria took
no notice of these reports. And scarlet fever was still
placed by the majority among the virus diseases. And
oh, the searches that were made and the reports that
were published on all sorts of false leads!

Then came the World War, that stopped all re-
search on scarlet fever as well as on most problems
not concerned directly with the winning of the war.

After that another group of workers opened up the
question of the specific agglutination of the strains of
hemolytic streptococci from scarlet fever and claimed
anew that practically all these strains fall into one
agglutination group.

Opposers to this arose as they did before, this time
including the authors, who showed that this did not

THE COCCUS FAJVIILY 93

hold when large numbers of strains of these strep-
tococci were studied. We showed that there were at
least four agglutination groups or types. This fact,
of course, did not detract from the claim that hemo-
lytic streptococci are the cause of scarlet fever, because
we know that among other kinds of bacteria one may
cause a definite disease, and yet among the strains
causing that disease there may be several agglutination
types of the bacterium.

Drs. George and Gladys Dick of Chicago, in the
meantime, had sho\STi that scarlet fever had followed
the implantation of strains of hemolytic streptococci
from scarlet fever into the throats of human volun-
teers. Thus, they added strong evidence to that given
by an earlier observation of ours that scarlet fever fol-
lowed the accidental swallowing by one of our labora-
tory workers of a small amount of culture of a hemo-
lytic streptococcus from scarlet fever. Just at this time
Schultz and Charleton demonstrated that convalescent
scarlet fever serum produced blanching or fading of
the rash when injected into the skin of a scarlet fever
patient in the region of the rash. And Dochez in New
York showed that the serum of a horse injected with
scarlet fever streptococcus in such a way that its toxin
would act throughout the horses would produce blanch-
ing of the rash in patients in the same way as would
convalescent serum.

Then came the crowning piece of evidence.

The Drs. Dick demonstrated by a new application
of an old test, the skin test discovered by Schick, that
the hemohi;ic streptococci from scarlet fever -wdthout
doubt manufactured an exotoxin that gave a positive
reaction, a little red spot, when a drop of a diluted

94 who's who among the microbes

solution vvas injected into the skin of a person sus-
ceptible to scarlet fever.

For a wonder, nearly everybody agreed that this
test works. Our minds had been prepared by the uni-
versal use of the Schick test. Then we all proceeded to
show that such a toxin could stimulate the production
of an antitoxin that seemed to work miracles in curing
scarlet fever. And thus, at last, the work of the Vien-
nese and Russian doctors and the other early re-
searchers was vindicated. But — ^there always seems to
be a but in this research work — ^but the close relation-
ship between all of the harmful strains of hemolytic
streptococci is still under investigation, and the end
looks far away. The reference hst of these studies
occupies many pages of our indexes.

The other large group of streptococci, those that
produce a green color when growing on blood agar
plates — the so-called green streptococci — are met with
in both disease and health even more frequently than
are the hemolytic streptococci.

Many of them are strong lactic acid producers, and
several are used as commercial starters and ripeners in
the manufacture of cheeses. As to the harmful vari-
eties, there is no question but that some are instru-
mental in causing certain cases of heart disease, sub-
acute and acute forms of rheumatism and septicemia.

Then there is the most noted member known of
this tribe, whose name alone is enough to send chills
down one's spine — the pneumococcus, the most com-
mon cause of all pneumonias, and the only cause of the
most dangerous type. Ah, the tragedies this coccus has
incited and is still inciting, the sudden attacks, the
horror of gasping breath, then death within a week!

THE COCCUS FAMILY 95

No wonder certain wealthy people are providing funds
for carrying on more investigations concerning the
different varieties of pneumococci, the kind of anti-
bodies they stimulate, and, most of all, how to make
these antibodies or serums so pure and strong that
they will have a quick curative effect; for they must
act very quickly to be effective in this disease.

The pneumococcus, Hke so many of the microbes
that may be pathogenic for humans, has compHcated
its relationsliips to man by having a number of types
each of wliich stimulates in any susceptible animal the
production of antibodies that act only on their own
type of coccus.

You may ask, "Why not have a mixture of the anti-
bodies?" That is what we are trying to get. But our
endeavors are further complicated bj'^ several things.
First, there are a number of pneumonia* cases due to
pneumococci that do not fall into any of the types that
are affected by the antibodies we have so far produced,
and we don't want to give serum unnecessarily.

We are classifying now the pneumococci of all of our
pneumonia cases that do not respond to the type
serums we already have, In order to find new types.
Miss Cooper, in our laboratories, has just found sev-
eral new types and is starting to produce antibodies to
combat them. It would be impossible, of course, to treat
every case with the right kind of serum. So many dif-
ferent varieties of pneumococci exist that one cannot
hope to have a completely polyvalent antibody solution
that will cover all.

The second difficulty is that not all the types of
pneumococci produce antibodies of equal potency. The
very ones that cause the highest percentage of deaths

96 WHOS WHO AMONG THE MICROBES

in those attacked produce the weakest antibodies. We
are trying every means we can devise to make anti-
bodies stronger. We have partly succeeded. Fortu-
nately, the type that stimulates the best serum is the
one that occurs most frequently in this country.

Leading from this is another difficulty, which you
may already have thought of. This is that if we want
the best effects of the strongest serum, we must know
the type of the pneumococcus that is causing that
particular case of pneumonia. In order to find tliis out
the spuium has to be sent to the laboratory to be sub-
jected to a series of tests.

And lipre we meet with the several difficulties of
identification. For this coccus also has a number of
forms that are not pathogenic for humans or other
animals, and as these are frequently parasitic in throats
of healthy people and might be growing along with
others, they must be excluded. Indeed, this coccus was
introduced to us first, as were a number of our
microbes, while living in a normal human being — ^this
time in the sputum. Dr. Sternberg found it in 1880
while examining his otmi spatum. Then he examined,
as a control for some investigations on malaria, the
saHva of a number of healthy students and found
similar cocci in several of the samples. Of course, the
pneumococci he found were grooving as parasites in
the mouths- of these hiftnans, but they had potential
pathogenicity.

The chief morphologic mark of identification of
these cocci as a genus is the formation of a mantle or
capsule about them. A second clear-cut point of generic
distinction is that bile dissolves them. But in order

Injecting pneumonia sputum into the belly of a white mouse to help
detennine type of pneumococcus

Drawing blood from horse that contains pneumococcus antibodies

STEPS IN THE PROCESS OF CONCENTRATING AND REFINING ANTITOXIN

Filtering after precipitation

Filtering through paper pulp

THE COCCUS FAMILY 97

to tell which type of serum must be used in any given
case we must first get our pneumococcus in pure cul-
tures, which we do bj- injecting the saliva into the belly
of a mouse, where the coccus grows so quickly that we
can recover a practically pure culture of it in a few
hours. Then we use the agglutination or precipitation
test. All tliis takes time. So we give our patient a dose
of our polyvalent serum first, and as soon as we find
out which type of coccus is attacking liim we change
to that type of serum if we have been able to produce
one that is potent.

Now we come to the members of the coccus family
that have been placed in the third tribe. Tliis tribe is
named after the man Xeisser, who first saw the chief
of the tribe. Adding to his name, as usual, the Latin
termination used to indicate tribe, we have the word
Neissereae as the name of this tribe. There are only two
members that are important to man. These are strict
parasites and have an insidious pathogenic action.

They have a few near relatives, who are of no great
importance, except sometimes, as may happen in all
families, to interfere with the identification of the im-
portant ones.

The chief of this tribe was first seen by Neisser
(1870) long before it was isolated in pure culture by
Bunmi (1885). It is a distinctive looking coccus, one
of the few that can be recognized under the micro-
scope when taken directly from the individual affected.
It almost always grows in pairs, each elliptical with
flattened side closely apposing the other. For this rea-
son it is often called the biscuit-shaped coccus. These
pairs are more or less equally spaced from each other

98 who's who among THE MICROBES

when they grow in their host's cells. When stained with
a double stain the pairs show up very well. They are
decolorized by Gram's method of staining.

This coccus is extremely fastidious in its require-
ments for growth. It is one of the most capricious of
microbes. It must be planted on very special media
at frequent intervals which must be quite regular. Fur-
thermore, the temperature at which it is growing must
not materially vary.

Neisser found this coccus in the pus cells of dis-
charges from humans suffering from a disease called
gonorrhea because it affects so often the genital tract.
For this reason Neisser called this germ gonococcus.
Its latest scientific name is Neisseria gonorrhoeae. So
far as we know, it grows only in human beings and is
practically only transferred by direct contact. It dies
very quickly outside of the body. While it chooses the
genito-urinary tract for its chief dwelhng-place, it
has a second site of election in the lining of eyes, espe-
cially of new-born infants. It was the chief cause of
infantile blindness before the use of silver nitrate solu-
tion dropped into the eyes of the new-born babies.

In those early days both nurses and doctors occa-
sionally contracted a fatal blindness through infection
with this germ. Tliis occasionally happens yet to the
careless. It sometimes passes into the general blood
stream and causes severe arthritis or inflammation of
the joints. It attacks the hosts, as do others of this
family, by producing a poison in its body, an endo-
toxin, that is released on its death. It grows in the epi-
thehal cells of the mucous membrane of its host, and
causes by its irritation the accumulation of the white
cells which may take up many of the cocci, so that some

THE COCCUS FAMILY 99

cells may be full of the characteristic, spaced, biscuit-
shaped cocci. It is because of this appearance that we
can make a microscopic diagnosis of the disease in a
short time.

This organism has come into great disrepute, but
its hosts are often innocent victims. The disease it
causes is classed as one of the two great venereal dis-
eases. The other is syphilis, whose cause belongs in
another family which will be introduced later.

The second member of this tribe looks very much
hke its chief, but its individuals when growing in pairs
are more spherical than elhptical, and one of them is
apt to be a little larger than the other and to stain
more faintly. It, too, readily gives up this stain by
the Gram's method. It is fastidious in its food needs,
but grows a little more easily than does the gonococcus.
It hkes the nerve tissue membranes (meninges) to grow
on. It also likes the back of noses and throats (naso-
pharynx) to hibernate in. There it staj^s growing slowly
in the occasional carriers, and when it gets to a person
who is susceptible it passes into the linings of the brain
and spinal cord and grows there, causing a purulent
inflammation. It is called meningococcus, or, according
to the latest classification. Neisseria intracellularis.

There seems to be much natural immunity to it,
since few cases occur. But once in a while there is a
small epidemic, or occasionally quite a large one. It has
never been found in lower animals, so the occasional
human carrier must be the starter.

Since it grows over the membranes of the brain and
cord it is hard to reach for treatment, and for years
many of the people attacked died. Then Jochmann in
Europe and Flexner in our country found that if the

100 WHO S WHO AMONG THE MICROBES

serum of animals fully immunized by the cocci was in-
jected very directly into the spinal canal of those at-
tacked many more recovered than those not so treated.

In this tribe, too, the individual strains vary in their
faculty of stimulating the production of antibodies,
and we have had difficulties in getting serums that will
have equal power to cure in these cases.

We have no clear-cut test to show the power of this
serum, as we have with the diphtheria antitoxin, so we
have to rely upon several potential tests which do
not always give us results that we can rely upon.

In giving this serum to a patient we make tests to
find out if he is suffering from meningococcus infection.
The spinal fluid that is drawn off is submitted to a
number of examinations in the laboratory, including
the hunting for the meningococcus.

CHAPTER MI
THE NITROGEN-USING FAMILY

Soil microbes — Life-giving forms in the life cycle of plants
and animals — Oxidizers of simple chemical combinations.

We have already pointed out the kno\\Ti fact that all
bacteria, as well as other forms of hfe, use nitrogen to
supply a fundamental need in their growth. The bac-
teria of the nitrogen-using family, which make up
perhaps the most important part of the microbic popu-
lation of the soil, are noted for using nitrogen in its
simplest combinations. More striking still, some of them
use and fix atmospheric nitrogen directly, thus per-
forming, merely by simply growing, an act that man
has only been able to accomphsh after many attempts
and through the use of very powerful physico-chemical
agents and electric machinery.

The nitrogen-fixing bacteria have also been called
the life-giving bacteria par excellence. And these mar-
vels among microbes justify this thrillingly significant
name. Without bacteria of tliis type, existence of Uving
forms on our earth as we know it would cease. From
the beginning of time these chemists of the soil (as all
soil microbes are called that take part in the life cycle
of gro^i:h of plants and animals) have probably been
utihzing their chemical powers, some to oxidize am-
monium compounds to nitrites, others to oxidize nitrites
to nitrates ready for plant absorption, and still others,

101

102 WHOS WHO AMONG THE MICROBES

perhaps the most important, certainly the most sur-
prising of all, have been actively engaged in absorbing
atmospheric nitrogen and making it a part of their
protoplasm — fixing it — thus placing it in such chemi-
cal combination that it can take part in the life cycle
again.

This last group of microbes, therefore, stops a so-
called leak of nature, the loss of nitrogen from the
soil to the atmosphere as inert nitrogen gas, after the
complete breaking down of nitrogenous material
through its various stages into nitrogen and water.
This "leak" would be disastrous to Hving forms if it
could not be stopped or if there were no way of making
this inert atmospheric nitrogen again available for
plant food. This is the very tiling that nitrogen-fixing
bacteria do. Some use the nitrogen directly as they
grow freely in the soil and others as they grow in
certain plant roots.

It had long been known that certain plants belong-
ing to the legume family, such as peas, beans and
clover, have along their rootlets Httle nodules which
were first thought to be diseased growths like galls
(Malpighi in 1687) on other plants. Then it was ob-
served that the plants that showed these nodules grew
larger and better in every way than did those that
had no such tubercles, and that the soil that grew
these plants and had them plowed into it seemed richer
than soils that used other "green manure." This led the
farmers to use clover on their farms to help restore the
fertihty of the soils. But it was not until the latter part
of the nineteenth century that the role played by these
root bacteria in restoring nitrogen to the soils in
usable combinations was fully demonstrated.

THE NITROGEN-USING FAMILY 103

It was first shown that in steriHzed soil no plants
finally grew. Then it was shown that if leached water
from soil that was growing legumes well was poured
over this steriHzed soil before all the plants trans-
planted to it were dead, the dying legumes recovered
and grew well, but other plants did not. Along with
the growth of the legumes appeared the httle nodules.
Then the Httle rodlets and ovoid bodies wliich filled
the nodules and which had already been seen by several
observers began to be studied more closely. In 1888
a German, Beyerinck, obtained a pure growth of these,
and Prazmovski, in Russia, and other investigators in
different parts of the world showed how the organisms
enter the root hairs of the young plants, pass through
the ceU walls, stimulate the formation of nodules and
cause the whole plant to grow vigorously. It is most
interesting to follow the progress of these investiga-
tions step by step and see how minutely the work had
to be controlled or checked up at each step to rule
out error and false deductions. The relation of the
organisms to the plant in which they grew was shown
to be a true symbiosis — that is, a growth where each
helps and is necessary to the other. It was found later
that there were several varieties of these nodule bac-
teria, some better for certain legumes and others for
other legumes.

In the meantime Winogradsky, a Russian, had
found an anaerobic bacillus, or one growing without
air, that had quite marked powers to fix atmospheric
nitrogen directly. This is a spore-bearing bacillus that
belongs in another family. It goes by the name Clostri-
dium pasteurianum, or Clostridium butyricum. We will
speak of its other uses later.

104. WHO S WHO AMONG THE MICROBES

Then Beyerinck found a large group of aerobic
bacteria in our nitrogen family that could also fix
atmospheric nitrogen directly.

When these bacteria were grown in a culture medium
containing only water, sugar and some mineral salts
but no nitrogen it was found that, as they grew, nitro-
gen was demonstrated in such cultures in amounts cor-
responding to the loss of nitrogen in the measured
quantity of air in which they grew.

It has been found since then that the ability to fix
atmospheric nitrogen is possessed in some degree by a
number of species of bacteria and by certain molds, but
that the two groups just mentioned, especially the
latter, are the chief direct nitrogen fixers.

While the fixing of free nitrogen in such a chemical
combination that it can be used by plants for food
is an important and dramatic act, other members of this
family have different powers over nitrogen in com-
bination that produce equally important, if not such
dramatic, actions in carrying on the cycle of Hfe on
our globe. We have already mentioned them. They
are the bacteria that oxidize ammonia or ammonium
compounds into nitrites and others that oxidize nitrites
into nitrates, ready for absorption through plant roots.

Pasteur (1862) was the first who suggested that
microbes play a part in the production of nitrates
in the soil, but it was not until about 1880 that the
mystery of the cause of nitrate production in soils w^as
cleared up. It was found (first by Schloesing and
Miintz) that when dilute solutions of ammonia w^re
passed slowly through long tubes filled with soil, the
teachings contained nitrates in amount corresponding
practically to the quantity of ammonia used. If this

THE NITROGEN-USING FAMILY 105

soil in the tube was first sterilized, by heating or by an
innocuous chemical germicide, the ammonia passed
through unchanged. Then if to this sterilized soil was
added a Httle unsterilized soil, the leachings again con-
tained nitrates. This was proof that there was some-
thing in the soil that was destroyed by heat, or a chem-
ical germicide that changed ammonia into nitrates.

The investigators concluded that microbes were the
things to hunt for, so they isolated in pure cultures
various bacteria, yeasts and molds that were in the
soil, and added each to the sterile soil in the tube, but
the ammonia passed through unchanged.

For a dozen j-ears many more than a dozen microbe
hunters tried to find a single kind of microbe that
would cause nitrates to come out of the tube in the
leacliings.

At last, Winogradsky was able to find out why they
had all been unsuccessful in their search. They had
been using the \NTong kind of culture media. He showed
that these special bacteria would not grow on any kind
of the common nutrient culture media.

Instead of the comparatively rich nutrient gelatine
medium that the others had used, he used a siHca jelly
containing only a iew* inorganic salts. He found that
there were two bacteria that made the change, one in
each of two stages. The bacteria of the first stage, that
is, those that oxidized ammonia to nitrites according
to the formula NH3 + 30 = HNO2 + H2O might be
called nitrous or nitrite bacteria. Winogradsky gave
them the name nitrosomonas.

The bacteria causing the second stage of oxidizing
nitrous acid or nitrites to nitrates —
HNO2 + 0 = HNO3

106 WHO S WHO AMONG THE MICROBES

— known as nitric or nitrate bacteria, were called by
Winogradsky, nitrobacter and nitrosococcus.

A few other bacteria have been described that change
ammonia to nitrates, one even that oxidizes it directly
to nitrates, but the greater part of the work is done
by the species discovered by Winogradsky.

In order that these organisms may do their work of
oxidizing thoroughly, the soil must be in just the right
condition. It must have plenty of oxygen, the right
temperature and not too much moisture or organic mat-
ter, the right reaction to alkalinity (magnesium lime
should be added if necessary), certain mineral salts,
and no deleterious bacteria or chemicals present.

When ammonium compounds have been converted
into nitrates we are at a point where we may con-
veniently start describing the important events in the
nitrogen life cycle that joins plants with animals.

We may start at the stage we have just mentioned,
in which the nitrates are absorbed from the soil through
the roots of plants. These help to form proteins in the
green leaves of the plants, aided by sunhght and
chlorophyl. These two agents, chlorophyl and sunlight,
transform the simple nitrates, carbon dioxide and water
into living matter.

In the second stage, plant proteins are eaten by
animals and in part help form animal proteins, in part
are broken up into urea, and in part pass out as other
nitrogenous products which are unsuited for animals
and too complex to be used in this form by plants. In the
third stage, the urea and the other nitrogenous prod-
ucts discharged by living animals or locked up in dead
animals or plants are broken up by the bacteria of de-
composition into ammonia or its compounds and water.

THE NITROGEN-USING FAMILY 107

Some nitrogen is also set free at this stage, forming the
"leak" spoken of before. This process is called denitri-
fication. Other products of decomposition, such as car-
bonates and sulphates, are formed. ]\Iany bacteria, in
fact members from each family of microbes, may take
part in tliis compHcated process of decay or rotting.

In the fourth stage, ammonia is converted by the
nitrifying bacteria, as we described above, into nitrites
and nitrates.

Thus we must have decay to provide food for our
plants before we can have Hfe. The organic matter
in the soil must be spHt up or changed into simple com-
pounds before it can be used by the liigher plants, the
carbon returned to the air as carbon dioxide to be used
by leaves, the nitrogen to the soil as nitrates to be used
by roots, and a number of minor but equally necessary
changes, reactions and interactions, such as the oxygen
supply to the soil affecting the formation of carbon
dioxide, the supply of minerals necessary for the
gro^\^:h of various forms, phosphorus, sulphur, iron, cal-
cium, zinc, manganese, potassium and magnesium.

Micro-organisms take part, though not as directly
or regularly as they do in the nitrogen cycle, in chang-
ing all of these other elements from their combinations
in the tissues of plants and animals where they are
unavailable for plant food. Thus we may speak of a
carbon cycle, an oxygen cycle, a phosphorus cycle, a
sulphur cycle and so on. And all of these vary accord-
ing to many different factors in the soil. There is even a
group of these microbes the members of which are
capable of breaking up cellulose, the dense wood of
trees. Winogradsky found that by altering his sihca
culture medium a little he could obtain an almost pure

108 WHO S WHO AMONG THE MICROBES

culture of these microbes directly, just as he was able,
by other shght changes to get luxuriant growths of
different species that perform other marvels of de-
struction and construction.

It is little wonder that the study of soils has been
carried on so intensively, that the research workers in
agricultural stations devote a large part of their time
to the study of soil micro-organisms and their effects
upon crops.

In view of the fact that there are so many different
kinds of microbes competing with each other in the use
of the environment of the soil for their growth, it is
little wonder too that agricultural research workers
have been on the lookout for helpful microbes that de-
stroy harmful ones, and harmful ones that interfere
with helpful ones. We have only to read the re-
ports from the Department of Agriculture to realize
how far we still are from controlling plant diseases
due to microbes and how great are the losses to farm
crops from such diseases.

The complex nature of the soil and the important
results that may be obtained from the abilitj'^ to regu-
late and control its physico-chemical evolution and its
microbal population make it a fascinating subject for
study.

The modern agriculturist must be well versed in
soil and plant bacteriology as well as in a number of
other sciences if he is to take advantage of all the con-
ditions that may produce better crops.

By some classifiers tliis family is placed first in the
system of classification, because its members are able
to live on the simplest of foods; but since the adult
forms of their individuals are bacilH or rod-shaped

THE NITKOGEN-USING FAMILY 109

bodies, they must come after the cocci if we accept
the coccus as the simplest morphologic type.

Here we see again that the vexed question of classi-
fication leaves us more or less confused. There is no
confusion or uncertainty, however, about the knowledge
we have gained of the importance of the activities of
members of this family in the lives of the human family.
They certainly have been and are our friends.

A group of bacteria that perform a very individual
service for man is placed as a genus among the oxi-
dizers in this family. The members of this group oxi-
dize alcohol to form acetic acid or vinegar. They are
appropriately called the acetic acid bacteria. Their
generic name is acetobacter. They are an indispensable
part in the industry of manufacturing vinegar. The
scum called "mother of vinegar" that is often formed
in the vinegar used in the home is made up of these
acetic acid bacteria. If a little of this "mother of vin-
egar" is added to the home cider, and plenty of air
is given it to furnish the oxygen needed for oxidizing
the alcohol in the cider, the cider may change into
vinegar in a comparatively short time.

In the manufacturing of vinegar on a large scale a
device is used whereby the "mother of vinegar" is
spread over a large surface with maximum exposure to
air. A heap of shavings gives such a surface. Then
diluted alcohol is sprayed over this bacteria-covered
heap, and the bacteria get busy with their taking of
oxygen from the air and their adding of it to the al-
cohol as indicated in the equation

CH3CH2OH + 03 = CH3COOH + H2O.

CHAPTER VIII
MICROBES LIVING IN THE INTESTINES

The "long-life" microbe — The signal bacillus — The food-
poisoning group — The typhoid-d3'sentery group.

The intestinal canal of man is a great gathering place
for microbes. Several kind^ are always found here,
some species frequently and others seldom. Some pass
with the digesting food quickly through the coiled
length of the intestines, others linger by the velvety
corrugated walls of this long winding passage, finding
ideal conditions for groTvi;h in its Avarmth, food, mois-
ture and reaction. Some are helpful to their host by
producing substances that are harmful to other more
deleterious microbes; some are indifferent; a few, and
fortunately these are among those that are seldom
present, are harmful. Among these kinds all of the
great classes of microbes may be represented, but the
bacteria constitute the bulk of them; indeed, these, as
a result of their vigorous growi:h, form a large part
of the dejected fecal masses. It is estimated by dry
weight that from five to eight grams of bacteria, hving
and dead, pass daily out of the intestinal canal. This
means about a hundred trillion bacteria. Such a large
number can scarcely be realized, but their estimation
by bacteriologic methods is comparatively simple.

A definite quantity of the feces is shaken up in sterile
salt water and from this a series of dilutions is made

110

MICROBES LIVING IX THE INTESTINES 111

until one is obtained which is thin enough to show the
microbes well separated from each other, when a meas-
ured amount, as, for instance, one hundredth of a cubic
centimeter, is spread uniformly over a known area
marked on a glass shde. The film is dried, covered with
a thin solution of gelatine, fixed in methyl alcohol and
stained with a staining solution that differentiates the
microbes from the detritus. Then the germs are counted
under the microscope, their number multiplied by the
dilution used and their whole number estimated.

The regular port of entry of these teeming trillions
is the mouth. At birth the alimentary canal of a normal
baby contains no germs. A few hours later they begin
to appear, mostly entering through the mouth, a few
growing up through the anus. The cliief source is the
food and the drink. The microbes, however, don't enter
in trillions. The food and drink of infants usually con-
tain, or should contain, few germs. Adults, according
to Thom, may take in many germs on uncooked food
such as fruit, even though it is fresh and sound. After
the microbes have passed the defenses of the stomach
with its acid gastric juice, and of the upper intestine
with its shghtly germicidal secretions, the varieties that
find conditions good for them in that natural incubator,
the large intestine, make great strides in growi;h and
soon dominate any others that may have survived; so
while many kinds may die, the few that sui'vive go on
increasing to the enormous numbers given.

Wliat effects have these moving masses of microbes
on man ? Are they necessary to him in digesting his food
or in any other way.'' Or could he live without them?
Many research workers have busied themselves with
trying to answer these questions by studies on lower

112 WHO S WHO AMONG THE MICROBES

animals. After numerous trials a few experimenters
have succeeded in getting eggs of lower animals free
from microbes — eggs of cockroaches, of tadpoles, of
chickens, of turtles. Then the investigators tried to in-
cubate the eggs and hatch and rear the young in
sterihzed incubators, and feed them with germ-free
food. A few of these trials proved that it was possible
to rear these animals T\4th germ-free intestines. Baby
guinea-pigs and goats also have been obtained free
from germs (by Caesarean section) and reared in germ-
free surroundings. These have lived long enough to
show that animals may live without microbes, and some
interesting observations have been made on them. But
since the practical impossibihty of ridding our sur-
roundings of these ubiquitous miscliief-makers is aC'
cepted as a fact, the next question investigators at-
tempted to solve was. Can man control the bacterial
flora of the intestines.'*

It had been observed that the first predominating
microbe in a normal baby's intestines is a kind that
produces large quantities of lactic acid. IVIilk, which is
the baby's chief food, contains much lactose or milk
sugar, and these bacteria use this sugar as they grow,
breaking it up into lactic acid. It was found that cer-
tain types of organisms cannot grow in an acid medium,
especially the so-called putrefactive bacteria that are
supposed to help produce that much-discussed condi-
tion called "auto-intoxication." Certain distinctly
pathogenic germs also do not grow well in an acid
medium. IVIany studies have been made, therefore, with
the object of finding out ways of transforming intes-
tinal flora by implanting a helpful microbe of the lactic

MICROBES LIVING IN THE INTESTINES 113

acid type, with the hope of correcting certain types of
intestinal disturbances due to the putrefactive bacteria.
There are many varieties of lactic acid bacteria. The
kind that appears first in the intestines of babies fed
with mother's milk, known as Bactericides bifidus, does
not grow there so readily as the cliild becomes older.
In the search for kinds that will grow readily and re-
main at home in the intestines supplanting other forms,
Metchnikoff called attention to the fact that Bulga-
rians are a long-hved people and that a common article
among their foods is a sour milk. They use as a starter
for coagulating their milk a certain lactic acid bac-
terium that came originally from "yoghurt." Metch-
nikoff obtained pure cultures of this starter, and the
laboratories throughout the world obtained subcultures
of it and recommended it for trial to those who suffer
from intestinal putrefaction. But alas ! those who took
this culture continued to suffer from "indigestion."
Lactobacillus bulgaricus, as it is called, while it grows
well in cow's milk and mare's milk, will not grow to any
extent in the human intestinal canal. It will not sup-
plant the putrefactive bacteria there. Thus this "bacil-
lus of long hfe," as it was called, has lost its reputation.
But the experimenters didn't give up the search. They
proceeded to study the lactic-acid-producing bacilli
found in normal human beings. They discovered that
one kind called now Lactobacillus acidophilus produces
more lactic acid than does any other bacillus found in
the intestinal canal of man. This has seemed to work
well in a number of cases of human auto-intoxication.
Cultures are supphed in milk and also in compressed
tabloid forms covered with chocolate. Though these

114 WHO S WHO AMONG THE MICROBES

tablets are very pleasant to the taste, they are not
considered as effective as the acidophilus milk. The
patient should be put on a minimum protein diet. There
is some doubt as to whether a true implantation occurs.
It usually takes time, many of the bacteria and much
lactose or milk sugar for an apparently successful im-
plantation. The great majority pass through the in-
testinal tract and are voided. That Lactobacillus acido-
philus is a helpful microbe, however, in some cases,
seems reasonably certain. Several different kinds of
energetic lactic acid producers are used in industries
for the making of sour milk products, but none of the
cultures have been successfully implanted in humans.
The milk in this form, however, may be more easily
digested by some people.

Very little is known about how much some of the
other microbes that are usually found in the intestinal
canal help keep the balance of normal microbic growth
there, but for the most part the others seem to be
quite indifferent to man's welfare, except on those few
occasions when one takes on a shghtly virulent quahty.
One of the varieties, however, called the colon bacillus,
or B. coh, a well-known member of the tribe bactereae,
that is always present and usually in very large num-
bers, is of use to man indirectly in this way. It is easily
identified by a special test, and since its presence is a
sign of fecal contamination, this test is applied in the
examination of water, milk and oysters to indicate
whether these substances have been contaminated in any
way by sewage. This test is called the presumptive test,
and the bacillus might well be called the signal bacillus.

This bacillus was discovered in the stools of children
by a German named Escherich, as far back as 1886. As

MICROBES LIVING IN THE INTESTINES 115

many different relatives of it have been found, in both
man and lower animals, they have been grouped under
the generic name Escherichia, derived from the name
of the discoverer, so now this ubiquitous bacillus, this
B. coli, has specifically the high sounding name Escher-
ichia coli. This bacillus has about the same powers of
resistance to germicides as has its dangerous relative
the typhoid bacillus, hence it is used in testing the
strength of germicides against that type of germ when
one does not want to take the risk of using the typhoid
bacillus itself.

B. coh, hke all of this tribe, is a short Gram-negative
rod that moves irregularly through a liquid medium. If
a httle sugar, almost any kind except saccharose, or
cane-sugar, is added to the medium, B. coli in its growth
breaks up the sugar into simpler products with the
formation of gas. This is the kind of medium that is
used to start the work of detecting the presence of
B. coh in any material suspected of fecal contamina-
tion. In its production of gas, B. coli differs from its
more pathogenic relatives forming the typhoid-dysen-
tery group.

And this brings us to the few really harmful germs
that occasionally dominate the intestinal inhabitants, if
not alwa3^s in numbers, in the detrimental effects they
have on their host.

First there are those that are known technically as
the food-poisoning bacteria. There are two very dif-
ferent groups of bacteria that cause food-poisoning,
each acting in an entirely different way. One, called
Bacillus botuHnus, is a large spore-bearing bacillus
from the soil that may be carried in vegetables and
fruits, and because of its resistant spores may not be

116 WHOS WHO AMONG THE MICROBES

killed, unless cooked for a long time at high tempera-
ture. It grows better when air is excluded (under
anaerobic conditions), so if sufficient heat to kill the
spores in the material has not been used in canning
these products, tliis bacillus may grow very well later
in the air-tight cans and produce a potent toxin that
may quickly kill human beings. We will tell more about
this bacillus in a later chapter when we introduce the
other spore-bearing anaerobes.

The other group of food-poisoners belongs to the
tribe we are describing here, one of those that may be
truly called intestinal tribes. This group has been
given the general name Salmonella after Salmon, an
American who mth Smith studied this group in the
early days of its discovery. Its members are so closely
related to the typhoid group that they are called the
paratj^phoid group, para meaning at the side of or
near. They are near relatives. They are distinguished
from the typhoid bacilli by forming gas in certain
media, and more especially by their fermentation of the
sugar rhamnose. They are different from the coli
group in their inabihty to ferment the sugar lactose.
They all look very much ahke in form and staining.

A number of intermediate strains have been described.
Indeed, there have been so many varieties described
that in the naming of the species there has been more
confusion than with any other group. The chief reason
for this is that members of this group are, perhaps
above all others, variable in certain traits. "Rough"
and "smooth" varieties described in Chapter V were
first discovered in this group. Mucoid and dry colonies
and still other kinds of colonies may be found in sub-
cultures from a single colony. Previous traits may even

MICROBES LIVING IN THE INTESTINES 117

be lost permanently. So the reports of each investiga-
tor concerning a stain were at first different in some
respects from those of others. The classifiers are trying
to correlate the various findings, and indi\adual in-
vestigators are working hard to help clear up some of
the apparent discrepancies.

That wonderful highly technical test, the absorption
of agglutinins, spoken of in Chapter IV, is rendering
great aid in throwing hght on the confused relation-
ships of this group of microbes.

Two members, called respectively paratyphoid A and
B, are essentially human pathogens, producing usually
a low-grade fever, something like t}^hoid fever. Krum-
wiede found quite a large percentage of normal human
carriers of these tj^pes, so there must be considerable
resistance to infection. In places where people from
several scattered areas of country are herded together,
as in camps during wartime, there is grave danger of
outbreaks of infection from these types, so they are
included with the typhoid bacillus in a vaccine recom-
mended to all people who are going to places where
they may be exposed to these bacilH.

They are all easily carried by milk, water, oysters
and other foodstuffs, and so they may be considered
food-poisoning bacteria, but the food-poisoners par
excellence, those that have produced the unexpected,
often fatal, outbursts of poisoning by food, are pri-
marily pathogens of lower animals, and they belong in
the majority of the outbursts reported to only one
species of this group.

This most common one is the variety first discovered.
It may produce inflammation of the bowels (enteritis)
in any of the animals we use for food, and in other

118 WHO S WHO AMONG THE MICROBES

animals, like rats, that might contaminate our food,
and thus get into man. This was called by Gaertner,
who first found it (1888), Bacillus enteritidis. It is
now called Salmonella enteritidis.

The second frequent poisoner is also a common type
causing infection among low^er animals, but it is more
often found in sheep, hence it is called the mutton type.
Its scientific or species name.'' — This is a big bone of
contention among classifying disputants. We may give
it the first name de Nobelle, its discoverer, used, Aer-
tycke, after the place where the first recorded outburst
occurred, and call it Salmonella aertycke. It is ingested
by man in eating insufficiently cooked infected meat,
usually mutton or lamb.

The third type that has been implicated in food-
poisoning outbreaks, though not so frequently as the
others, is called Salmonella suipestifer. This organism
was first found in hog cholera and for many years was
thought to be the cause of this disease, until de
Schweintz and his associates in 1905 showed that hog
cholera was caused by a filterable virus and that this
bacillus was merely a secondary invader. It may pro-
duce enteritis, however, in lower animals, and it has
been found in some cases of human poisoning from
food. Krumwiede found this form in a tapioca pudding
that had been contaminated with infected pork handled
by the one making the pudding.

Of course the strain found in the food eaten, the one
found in the source that contaminated that food, and
the one found in the people poisoned, must be identical.
Some very clever detective work must often be done
by bacteriologists to prove the case against a particu-
lar article of food. On the other hand, the cUnical his-

MICROBES LIYING IN THE INTESTINES 119

tory of an outburst of food-poisoning may be so strik-
ing that it may be sufficient to implicate a food source
of the microbe poisoner, even though the chain of evi-
dence may not be complete enough for proof.

For example, in the very first outburst where bacteria
were implicated, the classical one where Gaertner found
his bacillus Salmonella enteritidis, a number of people
came dovra with severe diarrhea and one died the next
day. Gaertner found that the only food these people
ate in common was beef from a cow that had been suffer-
ins from diarrhea when it was killed. The man that
died so quickly was one that had eaten the most meat
and eaten it raw ! He began to have symptoms of gastro-
intestinal disturbance two hours after eating. Gaertner
found his bacillus in the spleen of this man — and in
the meat of the cow — but even if he had not found this
bacillus he would have been sure it was the cow's meat
that had caused the poisoning.

The above incident illustrates several points In re-
gard to this type of food-poisoning. In the first place,
it shows that the amount eaten — that is, the number of
bacteria taken in — determines the degree of infection.
The man who died had eaten 800 grams. In the second
place, it shows that infection is due to the growth of
the bacteria through the tissues of man, rather than
to any exotoxin produced, as in the case with the spore-
bearing group of food-poisoners. This case also show^s
how quickly this type of organism may overwhelm the
individual infected with, massive amounts — symptoms
in two hours and death in thirty-six. The case further-
more demonstrates how carefully our food should be
inspected. In any sick animals bacteria may quickly
pass to all parts of the body. Finally, the case indicates

120 WHO S WHO AMONG THE MICROBES

that all suspicious foods, if they must be eaten, should
be thoroughly cooked.

The quickness of the killing action of certain of these
microbes on some people is still one of the many mys-
teries of the microbe world. Usually they haven't this
power, and not all people are susceptible to them when
taken in with food, so out of a group of people eating
food contaminated with these virulent varieties there
may be many who escape ; but there is no way of show-
ing who are susceptible or which varieties are danger-
ous. Hence, all of this group of bacteria must be con-
sidered potentially a source of danger. They may get
into unprotected food in all sorts of ways.

Rodents may be a source of infection. Thus, Krum-
wiede investigated an epidemic of food-poisoning fol-
lowing the eating of a cornstarch-cream-filled cake
where the filler was found to be contaminated with rat
droppings. Both the shelf where the filler had stood
uncovered overnight and the filler itself contained rat
fecal masses !

The last group of bacteria classed as inhabitants of
the intestinal canal of man, the most dangerous of all,
though fortunately not frequent, is the typhoid-dysen-
tery group, called Eberthella, after Eberth, who dis-
covered its most important member, the typhoid
bacillus.

The typhoid bacillus ! What a microbe for producing
tragic situations, the sources of which were long un-
suspected ! We mean those following in the wake of the
human typhoid carriers. For the typhoid bacillus is
one of the hngerers in a few human beings, fortunately
in only about 2 per cent, of those that have had typhoid
fever or come in contact with a source of infection.

MICROBES LIYING IN THE INTESTINES 121

It is bad enough to have typhoid fever, with its
swollen and ulcerated Peyer's patches (patches of
IjTnphoid tissue in intestines), its groT^-th of the germ
through other organs of the body, its irregular course
possibl}'^ ending in death ;* but to become a carrier, a
source of disease and death to others, is far worse.

One of the favorite resting places of the typhoid
bacillus is the gall bladder. In some cases they even
grow throughout the bile capillaries. The bile which dis-
solves the pneumococcus has no such effect on typhoid
bacilli; on the contrary; it allows them to grow in it
luxuriantlJ^ Once they reach the gall bladder and the
gall ducts through the capillary vessels, they may con-
tinue to grow there for an indefinite time, helping ma-
terially to produce the tj^phoid carrier.

Tliis carrier may be quite normal otherwise. There
is no way of telling that he is a carrier except bj^ a
highly technical and complex examination of his feces ;
or by the less certain and more harrowing way of fol-
lowing the trail of victims he leaves behind him. He
may live unsuspected in a community, unless he is at
all careless in liis habits, then the dire happenings in
his neighborhood point liim out in this day of enhghten-
ment as a suspect.

We all know the history of "Typhoid Mary." ^ But
it cannot be too often repeated, because it illustrates so
forcibly the great danger from carriers and the whole
question of the control of this insidious situation.

She was a cook. What a comment on personal habits,
particularly on the care that is taken of the cleaning of
hands ! Attention was first directed to her by Soper, who

*"T\pIioid Marv," bv George A. Soper, "Military Surgeon" for
July, 1919.

122 TTHO S WHO AMONG THE MICROBES

gives a thrilling account of her detection and handling.
Dr. Soper, who is one of our greatest detectors of the
sources of epidemics, particularly of typhoid fever, was
asked in 1906 by the o\Mier of an estate on Long
Island to investigate an outbreak of typhoid in his
home.

Six people in a household of eleven had been at-
tacked. No other case had occurred in that neighbor-
hood. That ruled out general water, milk and other
food supply: The individual water supply which the
people firmly beheved had been contaminated from the
cesspool, privy vault or stable manure pit, one or all,
was found on repeated examinations to give no evidence
of fecal or other contamination.

The family had eaten a great quantity of soft clams
obtained from an Indian woman living in a tent on the
beach, and it was thought that she had dug the clams
from polluted areas; but she also supphed other fam-
ilies who remained free from typhoid. That ruled out
the clams as a source.

After th'TS going over minutely every possible source
of outside contamination, including visits of members
of the family away from home and visitors to the family
before the outbreak, and excluding these, Soper con-
centrated on the immediate history of the household at
this time.

At last he found the clue that led to the solving of
the mystery.

The family had changed cooks about three weeks
before the epidemic had broken out. The new cook was
described as a tall, strong, healthy, intelligent silent
Irishwoman who knew how to cook, and the family had
been very sorry when she had said, about three weeks

MICROBES LIVING IN THE INTESTINES 123

after the outbreak, that she had to leave. As this cook
had come just at the right time for starting the out-
break, and as the histories of all the other members of
the family were found to be free from suspicion, Soper
determined that this cook, the now notorious "Tj^phoid
Mary," must be found. But she had completely dis-
appeared.

Soper finally traced her to a family where she was
acting as cook and where two cases of typhoid had
broken out several weeks after she had arrived. He
found that her reputation for silence had been well
earned. She would say nothing about her past. When
told she might be a dangerous typhoid carrier and that
her history and the examinations of her discharges
might clear up the situation, she indignantly refused
both. It has never been learned whether she had really
connected in any way the coincidence of typhoid cases
with herself, but her leaving whenever the outbreaks
occurred and her refusal to tell her history looked as
if she may have had some idea of the connection. She
insisted, on one or two occasions when she was pressed
to answer, that no one had ever suspected her. The
only incident in her life that she did tell about was one
that happened in a family she cooked for in 1902. Soon
after her arrival seven in this family of nine came down
with typhoid. Mary herself was one of the two who
escaped,* and the father of the family, who had had
typhoid early in^his hfe, was the other.

Mary stayed^ and helped take care (?) of all the
victims, and the father was so grateful to IMary that he
made her a handsome present. Mary added, "That
didn't look as if I was suspected, did it?"

It is true that until the time Soper took the situation

124. WHOS WHO AMONG THE MICROBES

in hand none of the outbreaks following Mary had
been attributed to her. They had all been investi-
gated (?) and their sources decided, so no one was
ready to incriminate Mary when Soper tried to find out
about her, and he had great difficulty in tracing her
history during those years. No facts pointing to her
having had typhoid could be ascertained.

Soper, however, considered her suspicious enough to
present her case to the New York City Health Depart-
ment. The officials interviewed her, and when she still
refused to have examinations made they compelled her
to go to the detention hospital on March 19, 1907.
There the necessary examinations were made. None of
her examiners who knew her history were surprised
when the laboratory experts reported that they found
her feces teeming with typhoid bacilli. Repeated
examinations of her stools on an average of three times
a week showed nearly always large numbers of typhoid
bacilli.

Thus it was proved that "Typhoid Mary" was a
hving incubator for the typhoid germs, and that her
soiled hands at toilet, insufficiently washed afterward —
if washed at all — were the means of conveying the
germs to her victims. In the outbreak that Dr. Soper
studied so minutely it was considered that the infec-
tious matter was carried by means of ice-cream con-
taining cut up peaches which Mary had herself pre-
pared. Here no heat sterilized'the fruit handled by her.

Mary was transferred to Riverside Hospital on
North Brother Island, where she was placed in a com-
fortable cottage and detained for three years. She was
allowed to receive friends and was given work to do that
did not endanger others. As this w^as one of the first

MICROBES LIVING IN THE INTESTINES 125

typhoid carriers detected in this country, the authori-
ties scarcely knew what was the best thing to do with
her. They suggested the removal of her gall bladder,
which sometimes effects a cure, but she refused opera-
tion. Her friends and "Friends of Liberty" interested
themselves in bringing legal action to have her re-
leased. But, fortunately for us, as you may know from
her subsequent history, they did not succeed. The health
authorities at the end of the three y^ears consented to
release her on her parole that she would not cook for
others, or in any of the ways she had been taught to
avoid in those three years be a danger to others ; more-
over, she was to report to the Health Department once
a month. She promised.

She kept her word for a while, then she disappeared
and was lost sight of for nearly five years, during which
time she assumed various names, so it was very difficult
later to trace her movements. Only two facts were found
out.

She lived for a time with a friend who finally came
down with typhoid. She was at a sanatorium in New
Jersey where two cases of typhoid occurred. They had
never had typhoid there before.

Then came the most dramatic demonstration in her
history and the one that led to her rediscovery.

In one of the most capably managed maternity hos-
pitals in the world an epidemic of typhoid broke out.
Twenty-five nurses and other attendants came down
with it. They had a fine cook kno\\Ti as Mrs. Brown,
who was jokingly called "Typhoid Mary" when the
epidemic began. This led some one to suspect her, and,
unknowTi to her, one of the doctors from the Health
Department who knew her was given an opportunity to

126 WHO S WHO AMONG THE MICROBES

see her. It was Mary beyond doubt. Arrangements
were made to capture her the next day. But by morning
Mary had disappeared again. She was finally traced
to a Long Island home, from which she had to be
forcibly removed to her old cottage on North Brother
Island, where she is to this day. She was considered too
dangerous and irresponsible to be allowed to go free.
Everything has been done for her comfort, and she
seems on the whole now to be quite willing to stay there.

Mary was known to have caused ten outbreaks and
fifty-one cases, among which was one death. She was
probably responsible for many more outbreaks, con-
sidering her habits. As some one said, Mary was a fine
cook, but she used indescribable spices.

The lessons to be learned from this first carrier to be
found in America have been well summarized by Soper
in his report already mentioned.

As a result of the facts learned from her life, the
Health Department has passed a regulation that all
food handlers shall be examined. Those found to be
carriers must be registered and are not allowed to re-
main in a business that might endanger others. We in
the New York City Health Department have registered
nearly two hundred chronic carriers. Notwithstanding
these controls, one of the food handler carriers recently
went back to his pushcart business and dealt out ice-
cream cones to school-children and others. As a conse-
quence, a small epidemic of typhoid broke out in that
neighborhood, which was quickly checked when the
carrier was recognized.

Various means have been tried to rid carriers of the
typhoid germs, but without much success. Of course,
vaccination renders the majority of people immune for

MICROBES LITING IN THE INTESTINES 127

a variable period. And as we said, this is advised for all
those in contact with carriers, or those who are about
to travel to regions that might be dangerous, or those
otherwise to be exposed to infection.

The great sources of danger from wide-spread epi-
demic infection by the typhoid bacillus are milk, water
and oysters. Danger from all of these is now minimized
by special methods carried on by most health au-
thorities.

The question of the use of typhoid vaccine was given
a marked opportunity of being tested during the great
World War. The results were unquestionably in its
favor. At the age of the masses making up armies,
from twenty to forty years, people are most susceptible
to infection with the typhoid bacillus, and the vast
majority of the troops developed no typhoid fever, a
condition that did not obtain during the Spanish War,
when the vaccine was used too late to be of ser^'ice.

The only other important group of human intestinal
pathogens is one composed of those that produce spe-
cific bacterial dysentery.

Many of the intestinal microbes were accused of
causing specific dysentery in man before Sliiga in
Japan, in 1898, found the right one that causes the
most severe cases. He called it Bacillus dysenteriae. It
is now known as Eberthella dysenteriae. The only dif-
ference in appearance between it and the typhoid bacil-
lus is that it is shorter and it is practically non-motile.
But it acts differently on sugars, and it also gives a
different clinical picture and causes the production of
different antibodies.

This is the chief of the group, but there are many
near relatives in different parts of the world. Park, who

128 WHO S WHO AMONG THE MICROBES

was the first to show that these relatives were different
from the true dysentery bacilli, suggested that these be
called Paradysentery bacilH, just as the near-typhoid
relatives are called Paratyphoid baciUi.

These paradysentery forms are seldom met with in
the United States, but the true dysentery bacillus is
found even less frequently. The paras are not very
virulent. But it is important to know that different
types exist, so that we may learn how prevalent they
are and be in a position to be able to trace any epidemic
that may occur. In Japan these types may cause very
severe epidemics.

Here, as in the identification of all other ultimate
types of germs, the absorption of agglutinins test is
used. In fact, it was by this test that Shiga, out of the
mass of germs in the stools of his dysentery patients,
was able to pick one that bore a relationship to the dis-
ease. Specific serum has been used with some success in
the cure of dysentery cases, and a vaccine has been
used as a preventive. Hygienic measures are carried
out in the same way as for typhoid carriers.

Among the infrequent and transient inhabitants of
the intestinal canal there is a small group of bacilli
that are somewhat hke the typhoid bacilli, but they do
not act like them on sugar media. They do not break up
any sugars. On the contrary, they make the medium
more alkaline, hence they are called alkalignes. Among
them is one that often reaches the intestines through
goat's milk. It was found by Bruce very frequently in
goat's milk in Malta and produced a fever called Malta
fever. This occurred especially in soldiers. A number
of people call these forms Brucella, after Bruce. Smith
and others think this bacterium, which is so very short

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MICROBES LITIXG IX THE INTESTINES 129

that it was first placed with the cocci, is a close relative
of a similar form that causes abortion in mares, cows
and s\\'ine. This variety is called Brucella abortus. They
are both related to a little bacillus that is often found
in dog distemper, though its pathologic relationship to
that disease is not yet settled. The majority of the
strains occurring in cow's milk are harmless in man,
but a few cause a disease called undulent fever. Nearly
a thousand cases have been discovered in the United
States alone.

Of course any pathogenic organism taken with the
food may start its infection in the alimentary canal,
and there are certain varieties that may assume dan-
gerous epidemic quahties whose chief site of action is
the intestines. A notable one among this type is the
cholera vibrio; but since this belongs to a different
group of organisms, it will be considered in another
chapter.

Theoretically, the disease-producing microbes found
in the intestinal canal are easy to contror so far as
transmission to others is concerned. All we need do is
to disinfect the discharges of patients and of carriers.

Practically, the carrying out of these control meas-
ures is not so easy. In the first place, each person who
has become infected with the typhoid bacillus, or with
any other one of these germs, must be detected early
in the disease.

The discharges may contain the bacilli even before
the patient comes to the doctor. Then the carriers must
be spotted. This detective work requires complex
laboratory tests which take time and experts to carry
out. Then we have to be sure that the attendants will
follow our directions in the cleansing of their hands

ISO who's who among the microbes

and of everything that comes in contact with the
patient's or carrier's discharges. We saw how difficult
it was to regulate this in the case of "Typhoid Mary,"
and we are sorry to say that there are many more as
careless as she.

In order that measures for the detection of carriers
may be carried out, health departments employ a large
number of milk inspectors, water inspectors and shell-
fish inspectors, and a large laboratory force to make the
required examinations of the samples these inspectors
bring to the laboratory.

CHAPTER IX

PASTEUR'S TRIBE

The "black death" bacillus — The ground squirrel or rabbit
disease bacillus.

This tribe, called Pasteurella, was given Pasteur's
name because Pasteur was one of the first to study the
cliief of the tribe and, wliile becoming acquainted ^-ith
it, to make a great discovery concerning its beha%aor.

The cliief, named Pasteurella avicida (avicida means
a killer of birds), is a small Gram-negative bacillus
that causes fowl cholera, or, as the disease is sometimes
better called, fowl plague. Pasteur accidentally discov-
ered when he injected into a fowl an old culture of this
bacillus, in place of a fresh one, that the bird became
sick ; but instead of dying, as did the fowls that had a
fresh culture, it recovered. Then, when Pasteur later
injected it with a fresh culture, most unexpectedly it
did not get sick at all.

Pasteur, thrilled with the thought that he had pos-
sibly discovered a new method of preventing fowl
cholera similar to the method of Jenner for the pre-
vention of smallpox, studied until he found out how he
could attenuate the culture and regulate its dose so it
would protect fowls absolutely from contracting the
disease. As a result of these studies he made a bacterial
vaccine which was the first bacterial vaccine ever used.

Each member of this tribe Pasteurella — and so far

131

132 WHO 8 WHO AMOXG THE MICEOBES

there are only seven members known — produces a simi-
lar kind of sickness, but each one has a fondness for
different kinds of animals. Some of them are scourges
of our laboratory animals, and many are the researches
they have interfered \\dth by killing off test animals
under observation. After the bacilli get into the body
of their animal host they grow quickly and abundantly
through the blood causing a septicemia. They also cause
hemorrhages into the tissues, so they are often called
the hemorrhagic septicemia group of bacteria. While
the bacillus of fowl cholera, Pasteurella avicida, may be
the classifier's chief of this tribe, it is not the chief of-
fender in attacks on human beings. In fact, so far as
we know, it never attacks humans. Only two of this
tribe do this, and one of these lightly and seldom; but
the other is truly a killer, a mighty power for evil to
human beings, one of the worst among the big patho-
genic microbes. For this is the microbe to which we have
referred in our first chapter as causing in olden times
those terrible wide-spread epidemics called the black
death. These epidemics practically put a stop to all
acti\dties of man except his taking care (and what
care !) of the sick, of the dying and of the dead ; or, in
his terror, his attempting to flee from his home and seek
less infected regions, often without avail.

Think of the influence this bacillus has had on the
world's history. Its beha\aor has occupied the attention
of more historians, doctors, bacteriologists and purely
literary writers than perhaps has that of any other
microbe. We all know Defoe's famous description of
the plague year of 1665. And other accounts of the
ravages caused by this microbe are met constantly by
readers of those periods of our world's history.

PASTEUR S TRIBE 13S

In the very earliest epidemics of plague recorded,
over half of a population died of the disease. It is esti-
mated that about twenty-five millions died of it during
the fourteenth-century epidemic. This was truly a
plague. The cause.'' The early people said it was the
same as that of all other plagues, the judgment of God.
Even if they had glimmerings of the part rats took in
the spread of the disease, they thought that the rats
were sent by God, and sacrifices or presents of golden
rats and buboes (emerods) were made in the tem-
ple to the avenging God (see Bible — I Samuel, V and
VI).

It was not until a comparatively recent epidemic
occurring in China, in 1893, that the very small but
powerful plague bacillus, as it is commonly called, or
more formally Pasteurella pestis, was discovered. Two
doctors, Yersin from France and Kitasato from Japan,
working independently, discovered it at the same time.
It is a short, comparatively thick Gram-negative bacil-
lus, and, hke all of this group, stains more intensely
at each end: that is, it is bipolar in its powers to ab-
sorb stains. It does not have the brilhantly stained
granules of the diphtheria bacillus, however. The
plague bacillus may grow in more irregular forms than
almost any other microbe, depending upon culture
medium and age. These appearances all help in identi-
fying the bacillus. Thus, if a httle more salt than usual
is added to the agar medium, the bacilH will show large
swollen forms that are full of vacuoles or bubbles.
Then in broth the bacilli grow in chains, looking almost
Hke streptococci. In the tissues they grow usually as
bipolar-staining, short bacilli. At the beginning of the
disease there are enormous numbers of these bacilli

134 WHO S WHO AMONG THE MICROBES

growing throughout the whole body. But they quickly
swell up and dissolve in older lesions, so they may not
then be demonstrated so easily. Usually cultures may
easily be obtained from the inguinal or groin lymph
glands, which are swollen, forming what are called
buboes. Hence, the name bubonic plague is sometimes
given to the disease. The fact that only this bacillus
was found in all the tissues of people dying of plague,
and was not found in any other disease, was strong evi-
dence that it was the cause of the disease. But tragic
evidence was soon to be added to this. Among the young
investigators working in a laboratory in Vienna with
a pure culture of the plague bacillus, one came down
with a typical attack of the plague after a small wound
infection. He quickly died. The bacillus was recovered
in pure cultures from his swollen lymph nodes (buboes)
and other tissues. Thus it was accidentally demon-
strated that the smallest wound is sufficient to cause
infection and that a pure culture of virulent bacilh
may reproduce the disease. Since this first laboratory
victim, in different laboratories of the world an occa-
sional worker has infected himself while handHng pure
cultures of this bacillus. It may even be able to pass
through the unbroken skin.

For this reason the plague bacillus is one of the few
microbes that we do not allow to be given out of the
laboratory to other workers, except to the Federal
Public Health Service representatives and then under
extreme precautions. This microbe may retain its vital-
ity and virulence so long in the test tube, and it may
infect people so easily, that we can never be sure it can
be handled with safety except by the most trustworthy
workers. Again, what a commentary on our personal

PASTEUR S TRIBE 135

habits and on the insidious attacks of these minute
creatures !

We have a strain of plague bacilli in our laboratory
that Dr. Wilson kept under observation for years. He
found that it had lived fully ^'irulent in the test tube
for over ten years without transfer, and this bacillus
forms no spores. It is easily killed by heat and by the
usual germicides. But under certain conditions, as the
one just cited, it may hibernate for many years and
still retain its death-giving powers.

It was several years after the discovery of the bacil-
lus that the part played by rats and the rat flea was
fullj^ demonstrated. Thus, the deductions recorded so
long before in the Bible were shoA\Ti to be right ones.

The rat is now considered the chief host, the natural
host of the plague bacillus, and the rat flea the chief
carrier, or vector, transmitting the bacillus to other
rats and to man. Bitten by the flea, man usually de-
velops the bubonic form of the disease. In some people,
however, the bacilU may cause pneumonia. This is a
very \'irulent form, generally ending with death. As
with other microbic diseases of the lungs, the germs
may be conveyed to a new host by droplet infection. So
people suffering from pneumonic plague are particu-
larly dangerous to others, as well as in grave danger
themselves.

The name pest bacillus (Pasteurella pestis) is well
deserved. Even yet, with all our knowledge of its real
hosts and its chief vectors and of its avenues of escape
from these animals, as well as of ways of controlhng
them, there are still epidemics of plague in those coun-
tries where it is impracticable to apply this knowledge.

It is reported that 500,000 people in India annually

136 WHO S WHO AMONG THE MICROBES

suffer from plague. These, of course, are a constant
even if remote menace to the rest of the world. For this
reason health authorities throughout the world, espe-
cially at the chief ports, are on the lookout for infected
rats on vessels coming from infected countries.

While a number of rodents, perhaps all, are sus-
ceptible to the plague bacillus, only certain species of
rats and marmots in various parts of the world, and the
native ground squirrel in California, have been found
actually to be infected with this bacillus.

Two varieties of the black rat have been found in-
fected most frequently, but all animals found suscepti-
ble to laboratory infection are potentially dangerous;
and, without care in protecting people against contact
with such rodents and their fleas, risks of infection and
even of epidemics may be run.

The rat flea seems to be very fond of its own host,
which it scarcely ever leaves until the rat dies, or just
before the rat dies. The fleas feed up to the last minute,
and finally leave their dying host with their alimentary
canals containing a full meal of the host's infected
blood. Then they hop to another host, preferably the
same kind of a rat. If that isn't in their neighborhood,
any other rodent that may be present is chosen. They
jump upon man only when no rodent is near. Before
feeding on their new host the fleas regurgitate some of
the infected blood at the site of the bite and bacilli are
carried through the wound into the blood of the victim.
If this victim is a rat it may only have a light attack
and show no symptoms, or it may become quiet, creep
into a corner and die, or it may develop chronic infec-
tion with few clinical symptoms. On autopsy the diag-
nosis in the majority of the infected rats may be made

PASTEUR S TRIBE 137

quite easily Tsith the trained naked eye. In the acute
form all lymph nodes are swollen and may be hemor-
rhagic. The subcutaneous and muscle blood vessels are
engorged. The liver and spleen are enlarged, and scat-
tered through them are small areas of necroses or dead
tissue.

In chronic rat plague there are foci of pus through-
out the organs. The plague bacilli are recovered from
these lesions by cultures or by the inoculation of a
susceptible animal.

During and just after the World War we were so
fearful of ha\dng our rats infected by the sick rats and
their fleas that might be on vessels coming from infected
ports, that the United States Federal Health Service
obtained the cooperation of health departments at
various ports to examine the local rats in order to find
out the kind of rats in each neighborhood, the kind of
fleas thej" harbor, and whether any rats gave evidence
of being infected with the plague bacillus.

In New York City, which was one of the places
chosen for the examinations, we examined thousands of
rats and collected many more than thousands of fleas.
We found no infected rats and none of the fleas that
usually carry the plague bacilli.

In one of the southern ports a few infected rats were
found. This warfare against rats and fleas is the chief
measure necessary in the prevention of plague. Of
course, in countries where human cases of plague still
occur, the isolation of the patient is equally important.
A vaccine has been found to give some protection, but
the effects do not last for a long time^ so its use is
ad\'ised only in the face of an epidemic or for those
people going to plague-infected countries.

138 "WHO S WHO AMONG THE MICROBES

The other bacillus of this tribe that is infectious for
man and may occasionally cause his death is of great
interest to humans for a number of reasons. In the first
place, it was thought by IMcCoy, who discovered it in
1911, to be the cause merely of a plague-hke disease of
ground squirrels in Cahfomia. McCoy and Chapin
studied the organism and gave it the name Bacterium
tularense, naming it after the country Tulare where
the first infected squirrels were found. They found that
the squirrel flea could transmit the disease. Rabbits
have since been found to be quite frequently infected
with this bacillus. The chief interest in this subject lies
in the fact that when the habits of this bacillus were
very minutely studied and a determined hunt was made
for it to find out its geographic distribution, such as
has been done by Francis of the United States Public
Health Service, it was found to be not infrequently
infecting man, and a number of doubtful cases of sub-
acute human fevers were finally laid at its door.

Francis has given a clear description of all the chni-
cal tj^pes of this infection. He has called the disease
Tularemia, after the name given to the bacillus by Mc-
Coy. He found that it might be transmitted by several
biting insects.

This bacillus resembles the plague bacillus in its
abihty to infect laboratory workers. It seems to get into
the body of such workers very easily, usually in ways
that cannot be traced. As met vdth in humans outside
of the laboratory it usually occurs in marketmen, and
transmission is eif ected through the wound that is acci-
dentally made by the marketman as he skins and dresses
rabbits for the market, infected ones among them ; or it
may occur in the housewife or cook as she dresses such

PASTEUR S TRIBE 139

rabbits for the table ; or a hunter dressing rabbits at
the end of a day's hunt may infect himself. If any one
handles an infected animal and then rubs his eye with
his unAvashed hand, he may become infected through
the eye, developing the oculo-glandular type of the
disease.

!Man may also acquire the disease through the bite of
the horse-fly or the wood-tick, both of which are car-
riers. A few have developed the disease from the bite
of an animal, such as the coyote, just after the mouths
of these animals have become infected from eating
diseased rabbits. One case was of a mother who is be-
lieved to have contracted tularemia through the prick
of her thumb, received while dressing the primary sore
on her fly-bitten son.

Human cases have been reported in nearly all of the
States in the United States.

The symptoms begin in an average of three days
after the bite or wound. Then suddenly the infected
one has headache, vomiting, chills and fever. When the
regional glands are infected they are painful and begin
to swell. Then at the site of the wound an inflamed
papule appears, which soon breaks down, forming an
ulcer with a punched out appearance. When this heals,
scar tissue is formed. There may be nodules along the
course of the lymphatics in man. In about half the cases
the lymph glands suppurate.

Infection through the eyes may be very severe and
occasionally fatal. There are certain cases in which the
fever is the prominent symptom. These resemble
typhoid fever. The diagnosis may be determined by the
agglutination test. The disease runs a subacute course
of several weeks, then gradually clears up.

140 WHO S WHO AMONG THE MICROBES

Francis ^ sums up the Important points relative to
infection by this microbe as follows :

Laboratory workers handling this organism are al-
most sure to become infected in the long run.

Agglutinins are present in recovered cases. Abortus
and mehtensis cultures cross agglutinate.

The organism requires cystin for its best growth. It
is very pleomorphic, it penetrates the unbroken skin
and invades fixed tissue cells — the hepatic cells of a
mouse and the intestinal epithehum of tick and bedbug.
It is transmitted through the egg of the tick to the
next generation of ticks. It has a great variety of insect
and animal hosts.

Thorough cooking destroys the infection, thus ren-
dering an infected rabbit hannless for food.

Laboratory workers engaged in performing necrop-
sies of infected animals should wear rubber gloves and
should observe all other precautions to avoid infection.
Cooks, marketmen and hunters should wear rubber
gloves in dressing rabbits.

The treatment is symptomatic. Rest in bed is the
most important. Those who have had the most experi-
ence with the enlarged glands do not advise excision, or
even incision, until a very evident soft, thin place ap-
pears in the skin overlying the glands. No preventive
vaccine or curative serum has yet been perfected.

» "The Atlantic Med. Jour.," 1927, 30. 337.

CHAPTER X
BLOOD-THIRSTY TRIBE

(Hemophileae)

The intriguing influenza bacillus — The exciting whooping-
cough bacillus.

Blood-thirsty (or blood-loving, according to the
derivation of its scientific name) has a murderous sound
when apphed to any Kving beings, but as used to de-
scribe a prominent trait of these minutest of kno^vn
li^^ng forms the name has not such a bad meaning as
it might seem. The bacilli of this family are called
blood-thirsty or blood-loving because they like blood in
their culture medium, and imbibe it in their growi;h.
Indeed, one form cannot grow in pure cultures outside
of the body of its host unless it has some of the hemo-
globin of the red blood cells, or a similar substance, in
its food medium.

This form is the intriguing influenza bacillus or
Hemophilus influenzae, the chief of the tribe. We call
it intriguing because it was long thought to be the cause
of influenza, but now there are grave doubts as to its
power to incite that disease. A few trained bacteri-
ologists still beheve in it.

When, during the big epidemic of 1889-93, Pfeiffer
first saw immense numbers of this very minute bacillus
in the sputum of those suffering from influenza he
thought he had discovered the cause of the disease.

141

142 who's who among THE MICROBES

When he found it wouldn't grow in pure culture on
any of the culture media that he tried he was sure he
had a very mysterious unusual organism, and he con-
tinued his intensive study of it. He learned that it had
no motility, that it stained faintly, decolorizing by
Gram's method, and that it would grow along with
some other bacteria from the sputum, but it would not
grow alone. Finally, after many trials he found that it
would grow in pure culture on artificial food when
whole blood was added to its food. Then, after a very
painstaking series of experiments, he proved that just
one part of the blood was necessary for its growth, the
hemoglobin. This fact, that it uses whole blood in its
growth, is beautifully demonstrated when some of the
bacilli are mixed up in a drop of blood and, after
spreading the mixture over the surface of a nutrient
agar plate, are allowed to grow at blood heat (37° C.)
for twenty-four hours. If such a plate is taken out at
this time and examined under the microscope with a
low-power lens (magnified about 100 times), a brilliant
picture is seen. On a red background of blood cells are
scattered glistening white, rounded, slightly scalloped
areas. These are the colony growth of influenza bacilli
which have used up all of the blood cells in these areas.

To the naked eye these colonies look like minute
drops of dew scattered through the blood.

Since the time Pfeiffer first discovered his bacillus
the question of why it could only be made to grow in
pure cultures when blood was added to its food has been
the subject of many studies, during which some inter-
esting facts have been brought to light.

Thus Davis, Avery and others found that there are
two substances in the blood that have to be present

BLOOD-THIRSTY TRIBE 143

before the influenza bacilli will grow. Then they found
that these same two substances were in a number of
vegetables, and that good gro"wi;hs of the influenza
bacillus may be obtained if one of these is added to its
culture medium in appropriate mixtures instead of the
blood.

Avery also found that certain kinds of soaps have an
inhibiting effect on the pus-forming cocci but encour-
age the influenza bacilli to grow. This soap medium,
called oleate blood agar, has proved to be a great help
in isolating and identifpng this bacillus.

It was also found that tliis bacillus would grow more
luxuriantly if the blood that was added to the medium
was heated. The blood is poured into the hot melted
agar. The heat changes the agar to a brown color,
making the medium look as if it were made of chocolate ;
hence we call this chocolate medium. We keep all of our
stock strains of influenza bacilh on it.

When Pfeiffer first found his bacillus he was so sure
it was the cause of influenza that he called the organ-
ism Bacillus influenzae, and he tried to reproduce the
disease in lower animals with it. But all the animals
seemed to be quite indifferent to its influence. Then
other microbe hunters begun to find the same kind of a
bacillus in other diseases and even in normal throats.

What a disappointment this was to those who had
great expectations of getting help from it in combating
that scourge epidemic influenza! Pfeiffer and his fol-
lowers cried, "There must be many carriers of the
germ; that is the reason we find them so frequently in
other conditions." "But," retorted the doubters, "if
there are so many carriers, why do we not have cases
of 'flu' more often? And why do we only once every

144 WHO S WHO AMONG THE MICROBES

twenty-five years or so have a big epidemic of this
disease?" As these questions remained unanswered,
many came to the conclusion that this bacillus could
not cause epidemic influenza. That it has some patho-
genic power was conceded. They thought it might be a
good second poisonous invader in mixed infections and
that it might help to produce certain chronic inflamma-
tions. But as for this being the cause of the big pan-
demics that occasionally swept over the world, some-
times with liigh mortaHty — no, they objected, there
must be a special virus that could do that.

The opportunity to gain e\'idence as to its relation-
ship to epidemics came with the last great pandemic
during the World War in 1917 and 1918. This evidence
was obtained by workers in various laboratories. We
had plenty of opportunity at that time to study influ-
enza under ideal conditions for obtaining an epidemic
strain of this bacillus if it existed. Our hospital received
many groups of sailors from different ships, each group
having come down with influenza at the same time, and
a big majority of these cases had great numbers of
influenza bacilU in their sputum and nasopharynx. Be-
sides studying these cases, we made a survey and gath-
ered material from a number of camps while influenza
was sweeping through them. We, alas ! had many op-
portunities, too, for studying autopsy material.

We finally collected hundreds of strains of influenza
bacilli and studied them from a number of angles,
especially from that of their resemblances in serum
tests.

We reasoned that if this baciUus caused the epidemic,
then the strain from each case should give evidence of
specific relationship to the majority of the other strains

Hunting for plague fleas on rats, in New York City Port

New York Health Department worker aiding Federal Health Service
in its hunt for plague-infected rats

BLOOD-THIRSTY TRIBE 145

we had gathered. Certainly when one infected indi-
vidual transmitted the disease to a group, this should
be so. We appUed to each strain the serum test we have
already mentioned several times, the one used for the
identification of strains — namely, the absorption of
agglutinins — and we found that by this test practically
all of these strains were different. Therefore, we con-
cluded, they could not have caused the epidemic, pro-
vided these bacilli retain their characteristics — their
identity — on passage through human beings and after
they had been isolated from humans. Man}'^ investiga-
tions were made to show that this bacillus might, in test
tubes, quickly lose its virulence and other significant
properties ; but wliile some interesting observ^ations were
made, no decisive evidence was unearthed.

During this fatal pandemic many investigators
searched rigorously for some cause other than the in-
fluenza bacillus, but no one found an3rthing with spe-
cific significance.

Two workers at the Rockefeller Institute thought
they had discovered it when they found in some cases
of "flu" a very minute, filter-passing anaerobe which is
now called by the imposing name Dialister pneumo-
sintes. But alas! this must join the influenza bacillus in
not coming up to expectations. No one else has been
able to find it in influenza cases.

Further evidence against the influenza bacillus being
the cause of the pandemic was given by the results from
vaccinating \s"ith the bacillus. Such vaccinations seemed
to afford no protection whatever.

So the cause of epidemic influenza remains as deep
a mystery as ever, and we are still helpless in our
efforts to combat it.

146 WHO S WHO AMONG THE MICROBES

One interesting fact among the many brought out
during these studies was observed by Dr. Povitzky,
working in our laboratories. She found that nearly all
the strains of influenza bacilH from a certain type of
meningitis were related to each other. So we made a
serum from these strains, and it has been used success-
fully in some cases of this type of meningitis which
before tliis were always fatal.

There are several very near relatives of the influenza
bacillus, none of them of importance to man except the
one that has been accused of causing that very un-
becoming disease, "pink-eye," or acute contagious con-
junctivitis. This disease is now quite infrequent, so we
know very little about the serologic relationsliips of the
strains of influenza-like bacilH found in great numbers
in the infected eye throughout the attack. The bacilli
found in "pink-eye" have been called the Koch-Weeks
bacilli because Koch and Weeks independently were
the first to describe them.

There is another eye disease the cause of which is
laid at the door of a member of this tribe. This is called
angular conjunctivitis, because it begins in the angles
of the eye. The bacillus supposed to cause it is a little
bigger than the others of this tribe. It was discovered
by two men, Morax and Axenfall. It is therefore usually
called the Morax- Axenfall bacillus. The scientific name
given to it is Hemophilus lacunatus.

Another member of the tribe is the cause of soft
chancre in man. This, like all the tribe, will only grow
in very special media. In this case blood serum is the
best thing to add, and even then the baciUus makes
only an extremely delicate growth.

BLOOD-THIRSTY TRIBE 147

Now we come to the last member of this tribe, and
perhaps the most important from man's point of view,
now that the influenza bacillus has been relegated to the
background as an etiologic factor in epidemic disease.

This is the irritating whooping-cough bacillus, wliich
is considered the cause of that dreaded disease of early
childhood, pertussis, commonly kno^^Tl as whooping-
cough. This bacillus was not discovered until Bordet, a
famous Belgian doctor, assisted by Gengou, made a
minute bacteriologic study of Bordet's two children as
they were coming down ^^'ith whooping-cough, and con-
tinued studying them during the whole course of the
disease. They found early in the disease practically
only one kind of a bacterium in the sputum that the
cliildren coughed up directly from their air passages
during a characteristic paroxysm of coughing. This
was a minute. Gram-negative bacillus that looked much
hke the influenza bacillus, only shorter and more regu-
lar in length. Indeed, several investigators have thought
that the influenza bacillus was the cause of the whoop-
ing-cough.

Since the influenza bacillus often accompanies the
pertussis bacillus, it is not to be wondered at that these
germs were first mistaken for each other. But if they
are once separated from each other in pure cultures the
differences between them are marked. Bordet, at first,
could not get his tiny bacillus to grow. Then when he
added a large quantity of fresh blood to a potato broth
agar and streaked over its surface a Httle of the sputum
containing the bacillus, slowly after two or three daj's
minute grayish, almost pin-point, colonies appeared
along the streak. When a Httle of this growth was fixed

148 WHO S WHO AMONG THE MICROBES

and stained, it was found to consist of innumerable
minute bacilli like those seen in the direct stained film
from the sputum.

The influenza bacilli do not grow as well on this
medium as do the whooping-cough bacilH; moreover,
they darken the medium as they grow, while the whoop-
ing-cough bacilH Hghten it. The next and more marked
difference between these two bacilH is that after two or
three transplants on this medium the Bordet-Gengou
bacillus, as it is sometimes called, will grow slowly but
surely when transplanted to ordinary nutrient agar,
while the influenza bacillus will not.

Then another difference Povitzky found out in our
laboratory. If one adds just a Httle acid to the Bordet-
Gengou food medium the whooping-cough bacillus will
still grow well, while the influenza bacillus will not
grow at all. This is a very good way to isolate the
whooping-cough bacillus from the sputum when it con-
tains many influenza bacilli and other bacteria that
will not grow in an acid medium; and most wdll not.
There are still other points of difference between these
two germs, so now an expert bacteriologist has no difii-
culty in distinguishing between the two. The most
important difference of all is that nearly all the whoop-
ing-cough bacilh obtained from different cases are ahke
serologically, while the influenza bacilli are not.

Bordet tried to find out whether any of the lower
animals would get whooping-cough when he exposed
them to infection with his bacillus, but none of them
were at all disturbed by it. So he was not able to prove
that his bacillus was the specific cause of whooping-
cough by that method. Then he subjected the blood of
his children to a number of tests which were at that

BLOOD-THIRSTY TRIBE 149

time quite new. He used the absorption of agglutinins
test and the complement fixation test that we described
in our fourth chapter. By these methods he found that
as the children recovered from the disease their blood
contained specific agglutinins and specific complement
fixing substances. This was accepted as strong evidence
that his httle bacillus is truly the cause of whooping-
cough.

If it is, said the questioners, then a vaccine prepared
from it and injected into susceptible children should
give them lasting immunity, since one attack of the
disease does that.

So they proceeded to make a vaccine. The different
methods of making this vaccine and the varying re-
ports regarding its value both in curing and in pre-
venting the disease would fill a large volume. The vac-
cine as made so far has probably some influence in
preventing the disease, but it has very little, if any, in
effecting a cure after the disease has once started.

CHAPTER XI
THE RESISTANT FAMILY

(Bacillacese)

Spore-bearers in the soil — Forms resisting canning — Anthrax
bacilli — The lockjaw bacillus — War wound bacilli.

This is the great spore-bearing family, found chiefly
in the soil. Its members form spores or seeds that are
more resistant to deleterious influences than are the
spores or cysts produced by members of other classes
of microbes. They resist extreme heat or cold, prolonged
drying and sunlight, the action of stains and of many
chemicals.

They may indeed be called the resistant family.

Because of their power to resist destructive forces of
nature they are found wide-spread throughout the
world, in places where other varieties might not be able
to exist. Wherever there is dust, there may be these
spores.

They are the forms that so interfered with the clear
understanding of our early microbe hunters on that
mysterious subject, spontaneous generation, because
they persisted in the boiled infusions of peas, nuts,
meats and other substances used to demonstrate Hfe. It
took a Spallanzani, a Pasteur and a Cohn to prove that
the irregular results following heating were due to the
presence of resisting forms or spores.

But even they didn't realize how resistant to heat

150

THE RESISTANT FAMILY 151

some of these spores are. Certain varieties are reported
to have withstood boiling in water 100° C. for nineteen
hours. To be killed by heat in a much shorter time (one
hour) they need to be superheated under pressure
(310° C. or 600° F.).

It is the spores that we must be constantly on our
guard against in sterilizing our culture media. Inter-
rupted or fractional sterilization such as we described
in Chapter II for allowing the spores to grow out into
vegetative forms between sterilizations must sometimes
be used.

I\Iore important still is the fact that these are the
forms that resist the heat in the canning of our foods.
Not only are the spores found on the vegetables and
fruits we put up in our cans, but there are some espe-
cially resistant forms on sugar-canes. The canning
industries and the sugar manufacturers have spent
much time and money in investigating the powers of
resistance of these forms. The question of their thermal
death-point — that is, how much heat it takes to kill
them — has been determined for all the species met with
in these industries.

AMiile the fact that they spoil our canned foods is
important enough to occupy the attention of our can-
ners, a far more serious quality of some of these forms
occupies the attention of our phj'sicians and public
health officers.

This is that they may injure our bodies as well as
our foods and may do so to such an extent that death
may result. We have in this family two of our most
toxic destroyers of hfe and another one that destroys
by its gro^-th through the body of its victims. Then
there are other members that produce less virulent

152 WHO S WHO AMONG THE MICROBES

toxins and have less power to invade the body, but some
of them may kill for all that. None of these forms pro-
duce definite epidemics ; that is, they are not conveyed
easily from person to person, or animal to animal. In
other words, they are not contagious, but they or their
poisons are infectious. They are usually picked up by
the individual through wounds coming in contact with
infected soil, or they may infect through their poisons,
elaborate in infected canned goods or other preserved
foods, which may be taken in through the mouth.

The resistant family is divided into two groups or
genera chiefly on the basis of their behavior toward
free oxygen. The first group is made up of forms that
grow in the presence of oxygen — that is, they are
aerobes. This group or genus is called bacillus, which
means a httle rod. The second group includes forms
that cannot grow in the presence of free oxygen ; that
is, they are anaerobes. They are called clostridum,
which means spindle, because many of the varieties as-
sume this shape at certain stages of their growth.

In the first group all of the varieties but one are
either harmless saprophytes or they are indirectly help-
ful to man by the great activity they display in break-
ing down organic matter in the soil through their
powerful enzymes.

The chief of this group. Bacillus subtilis, is of in-
terest to beginners in bacteriology, because it is one
of the first bacteria given him to study. It is so harm-
less, so big, so easily grown and stained; it produces
such nice big spores so readily ; it is so motile with so
many big flagella. Moreover, it liquefies gelatine, pep-
tonizes milk, produces acid in certain sugar media and
hydrolizes starch; in short, it is a very useful and

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THE RESISTANT FAMILY 153

convenient microbe to have around in a classroom so
long as its spK)res don't find their way into places where
they are not wanted. A close relative of this microbe,
looking and acting much like it, only bigger, is also
used for classroom demonstrations. It is called Bacillus
megaterium. Both of these species look very much like
the only harmful one in this group.

This enemy of man and beast is called Bacillus
anthracis, from one of the names of the disease, anthrax,
wliich means a burning coal. It was given this name
because the animal affected usually has a burning fever
and a darkened, almost coal-black blood.

It does not attack man primarily. Its favorite hosts
are sheep and cattle. It also attacks horses and goats,
but not dogs, cats or birds. While man is susceptible,
he only contracts the disease through a wound or on
prolonged contact mth infected material.

This microbe is of great historic interest. It is the
first bacterium that was sho^sTi to be the cause of a
disease, the first microbe that was made to grow in
pure culture outside of the body of its host and, after
a number of culture generations, made to produce the
disease when injected into a susceptible animal.

As usual, several investigators working independ-
ently helped to bring out all these new facts. Koch and
Pasteur were the most active workers in this field. They
knew practically nothing about making artificial cul-
ture media then. So Koch used the tears of an ox, and
Pasteur used urine for cultivating this wonderful new
microbe. They found that the rods are non-motile and
that they grew out in chains of bacilli, end to end. The
opposed ends are slightly concave, giving a bamboo-
rod appearance to the chain. In gelatine, in which they

154 WHOS WHO AMONG THE MICROBES

grew it later, it has been likened to a miniature inverted
Christmas tree. In tissue it shows a capsule. It is Gram-
positive.

One should read the life of Pasteur ^ to get a vivid
impression of the enthusiasm and thoroughness dis-
played by him in these investigations into the cause
and cure of the diseases that affect masses of men and
beasts. At that time whole flocks of sheep were dying
of anthrax, or splenic fever, as the disease was also
called because the spleen became so big as the infection
progressed.

Certain fields where the flocks fed were thought by
the people to be accursed because nearly all the ani-
mals that went into them to be fed became sick and died.
Pasteur soon showed that these fields were indeed ac-
cursed, but not in any mysterious supernatural way.
He showed that the soil was full of anthrax spores
deposited there by the dying and dead animals. Even
if the dead animals were buried, as they usually were
superficially in the fields, Pasteur showed that the earth
worms feeding on them could take in their spores and
bring them to the surface of the ground. He also showed
that infection of fresh animals was hastened if the ani-
mals ate any irritating thing like prickly burrs.

Then Pasteur did a stiU more wonderful thing. He
made a vaccine from these microbes that, when injected
into susceptible animals, protected them against infec-
tion vnih the bacilli. That was another great day for
Pasteur.

He had just made his cliicken cholera vaccine. So
this was the second successful bacterial vaccine made,
both by Pasteur. The immunity following the anthrax

^ By Valleiy-Radot.

THE RESISTANT FAMILY 155

vaccine lasts about a year. All together, the measures
recommended and carried out by Pasteur reduced
anthrax materially in France. But o^ving to the im-
perfect working of the local health services in certain
parts of the world, this disease still exists. The skins of
animals that were infected with spores are used for
various purposes. Wool-sorter's disease is anthrax con-
tracted by workers handUng infected pelts. The hairs
of some of these pelts are used as bristles in shaving-
brushes, and during and just after the World War,
when many infected pelts were used, some of this ma-
terial slipped through into our country and a number
of people became infected with anthrax from such
brushes. We examined the brushes and found anthrax
spores in them. We recommended certain ways for
sterihzing these brushes, which are now carried out.

While Pasteur was studying anthrax and devising
ways for eradicating it, his attention was forced upon
another bacillus by his detractors. They said they
could produce a disease with anthrax bacilli in the
blood and yet not get any culture from it. Pasteur
worked over this situation. He was sure it wasn't
anthrax; but blood containing it caused a septicemia
in other animals, so he was equally certain that it was
a poisonous microbe. Finally, he thought that the
oxygen of the air might be interfering A\ath its growth
in artificial culture media. So he devised a way of
excluding the oxygen, and, lo and beliold! the thing
grew beautifully along w4th other microbes. It was an
anaerobe. The agar plate method of separating
microbes and getting them in pure cultures had not
come into use, so Pasteur onlj^ had the dilution method,
which didn't always work; but he was finally able to

156 WHOS WHO AMONG THE MICROBES

demonstrate clearly that this was an entirely different
microbe from anthrax. Pasteur named this new organ-
ism Vibrion septique, because it causes a septic condi-
tion. It also causes swelling of the tissues, helped by the
gas it produces. Koch found similar forms in animals,
with intense local swelling or edema, that he called
Bacillus edematis-maligni, but because he didn't get
pure cultures we can't be sure as to its relationship to
Pasteur's germ.

Pasteur called attention to the similarity of his new
large anaerobic bacillus to the one he had described
long before (1861) as causing butyric acid fermenta-
tion and which he had called Vibrion butyrique. This
was the first spore-bearing bacillus that was shown not
to be able to grow in the presence of atmospheric oxy-
gen. This then is the recognized chief of the genus
Clostridium or spindle-shaped anaerobic bacilli.

Of course, this type of microbe, with its resistant
spores and its frequent presence in the soil, was en-
countered often in the early days of bacteriology, and
each discoverer, thinking he had found a new germ,
described it under a different name. So now it has a
list of twenty-six synonyms to indicate the interest it
excited and the ignorance that existed in regard to its
various characteristics.

Little wonder that in the beginning of bacteriolo-
gic time people's ideas were mixed in regard to the
identity of an organism exhibiting such a protean ac-
tivity.

In the first place, it is one of those anergic fixers of
atmospheric nitrogen that the Russian Winogradsky
brought to light. Then it was used in producing butyric
acid by fermenting sugar and putrid cheese. One of

THE RESISTANT FAMILY 157

the salts of this butyric acid has a very pleasant smell
hke pineapple. It is called essence of pineapple and it
is used in making certain perfumes. It is also used in
making artificial rum and other spirits.

Furthermore, this bacillus breaks up cellulose, coag-
ulates milk, reduces nitrates, produces acid, gas and
alcohol with many different sugars. Such is the chief
of the spindle shapes.

It has a host of relatives in the soil and the intestines
of certain animals and, through these sources, in many
other places. Among them, as usual, there are some,
including the Vibrion septique, that are dangerous to
man. Two of these occupy a high place among the
microbe enemies of man.

One is the dreaded lockjaw bacillus, the one whose
spores lurk in garden earth, in the dust of streets, in
unclean sand piles, around stables, on rusty nails and
so on ; in short, wherever manure in any form can reach.
For these bacilli, the drumstick bacilli, so called because
they produce rounded spores at the ends of the rods,
make their home often in the intestinal canal of some
domestic animals, particularly of horses. Not only do
they grow in horses, thus making them carriers, but
they may find their way into man's intestines and re-
main there as a potential danger.

The reason these carriers do not develop lockjaw is
because they are immune to the tetanus toxin. They
have antitoxin in their blood, and the reason the bacilli
these people* carry, and no doubt distribute around
freely, do not cause lockjaw more frequently in other
people is chiefly because the lockjaw bacilli can only
produce their pecuHar and very powerful toxin under
special conditions, and because this toxin is poisonous

158 WHO S WHO AMONG THE MICROBES

only for the nervous tissue, and is only fatal if it can
get to the central nervous system over nerve tracks.

In other words, these bacilli, in order to prostrate
their victim wdth that violently spasmodic disease called
lockjaw or tetanus, must be able to infect through the
right kind of a wound for allowing them to grow and
manufacture their toxin.

Such a suitable wound must be dirty and ragged to
allow other bacteria to be introduced at the same time
so they may grow and use up the oxygen that is so
harmful to the tetanus bacilli and others of this group.
Among these associated bacteria, furthermore, must be
none that produce certain acids in their groMi:h, because
these acids may interfere with the production of the
tetanus toxin. When these fastidious tetanus bacilli
find just the right conditions, they grow quietly but
steadfastly in the wound, causing no apparent disturb-
ance there but manufacturing slowly and surely that
deadly* toxin which is absorbed by the motor nerves and
carried to the brain, where it accomplishes its distinc-
tive intoxication causing those violent rigid spasms and
usually the death of the victim in a short time.

So beware of dirty ragged wounds! These are the
wounds that occur so frequently in wars. And in the
old Fourth of July days, how many cases of tetanus
followed the wounds of the shot-up children ! Not only
are wounds that are caused by explosives more ragged
and more dirty than most other wounds, but gun-
powder often contains the spores of tetanus bacilli
carried in on the cotton gun-wads.

In the old days, too, of septic midwifery, there were
a number of cases of tetanus following childbirth, and

THE RESISTANT FAMILY 159

these may be common yet in those parts of the world
that are not reached by our laws of hygiene.

Ovs'ing to the ubiquity of the spores, special tests
must be made to preclude their occurrence in any of
our biologic products or in an}" of our surgical
dressings.

Fortunatel}'' for the careless or ignorant, these bacilli,
like the diphtheria bacilli, have been sho^^n by man to
be able \^dth his help and that of a susceptible animal
to provide their own prevention.

That powerful toxin of theirs, when injected in care-
fully graded, gradually increasing doses into a sus-
ceptible animal like the horse, will cause an equally
powerful antitoxin to be manufactured.

This antitoxin, when injected into any one imme-
diately after receiving a wound that might be infected
with the tetanus bacilli or its spores, is almost a 100 per
cent, preventive of tetanus. The injection must be
repeated at the end of ten days, as the antitoxin has
disappeared by this time and w^th it the immunity.

For many years, now, the health departments sup-
plying antitoxins and other biologic products to the
citizens send to the supply stations, just before the
Fourth of July, enough tetanus antitoxin to have on
hand for injecting in cases of firearm wounds. Since
the development of the "Sane Fourth," not so much of
this serum has been used, but plenty of it is still kept
conveniently near in case of need.

At the beginning of the World War, when the supply
of the tetanus antitoxin serum was low, many of the
wounded died of lockjaw. When the antitoxin was
rushed from all possible producing plants to the front,

160 WHO S WHO AMONG THE MICROBES

and began to be used freely and often, there were prac-
tically no more deaths from tetanus.

This antitoxin is used very frequently in veterinary
practice, particularly in the treatment of horses that
are so susceptible to the toxin.

In our o\\Ti work with animals we inject all horses
with a preventive dose of this serum before we start
them on their course of injections for the stimulations
of their various antibodies.

Prevention, then, is the great useful property of this
serum. A vaccine can be prepared from the toxin by
adding a small percentage of formalin and allowing it
to stand for a month at body temperature. Its injection
causes no bad effects; on the contrary, it causes an
active immunity to develop. If we ever have a great
war again Me will probably vaccinate all the troops,
just as we now do against smallpox and typhoid fever.

Cure is another matter. After a person once shows
symptoms of tetanus his cure is doubtful. It used to be
in greater doubt than it is now since we have learned
that if the serum is injected into the spinal canal it
reaches and neutrahzes the toxin much more effectively.
So now only one quarter of these victims of tetanus die,
while before the intraspinous method of injecting the
serum came into use fully half of these became rigid in
death.

The other dangerous enemy of man in this group is
the one that causes those spectacular cases of food-
poisoning known as botulism, so called because the first
cases described in the latter part of the eighteenth cen-
tury followed the eating of certain sausages. Many
cases called ptomaine poisoning were no doubt caused
by this bacillus.

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Diphtheria bacilli showing large club-shaped forms. Grown
on nutrient agar for 48 hours. Magnified 2000 diameters

Comparative colony growths from clean and dirty milk,
grown in nutrient agar in Petri dishes. Reduced to one
third diameter

THE RESISTANT FAMILY 161

After the bacillus (Clostridium botulinum) was de-
scribed by Van Ermengen in 1896, and its character-
istics studied, it was found to be wide-spread in nature.
It has been isolated from fruits, hay, vegetables, from
the feces of various animals, and from garden soil in
different parts of the world.

From these sources it gets into our food, and if its
spores can develop there, its highly potent toxin may
be formed. It grows without air, so if the spores have
not been killed, our air-tight canned foods may be ideal
places for it to grow. It doesn't produce any smell in
its growth, so we cannot detect its presence by means
of our noses as we can other putrefactive microbes. It
has been found in canned olives, beans, asparagus, corn,
spinach, pears, apricots and beets, besides being traced
to cheese and to sausage and other preserved meats and
fish. This is one of the poisons that may not be de-
stroyed in the stomach.

The house^dfe's chief protection is in boihng any
foods that have the slightest suspicion of being infected
with tliis bacillus. The poison is killed by fifteen min-
utes' boiling. KnowTi infected food should be barred.
If tlii'own out to animals, they too may be poisoned.
Chickens may get limber-neck. Hogs, horses, cattle and
goats have been shown to be susceptible. People and
animals infected show more or less rapid symptoms of
paralysis.

An antitoxin has been produced which prevents the
action of the toxin in experimental animals, but it does
not have much influence in curing a case in man or
beast showing definite symptoms of botuHnus poison-
ing. The remedy is applied too late.

Another member of these poisonous soil spore-bearers

162 WHO S WHO AMONG THE MICROBES

grow'ing only without air is one that so far has not been
found in man, but it produces a disease called quarter
evil or black leg or symptomatic anthrax in sheep,
cattle and goats. Other domestic animals and man seem
to be naturally immune. A vaccine was prepared by
Arloing, after the manner of Pasteur's vaccine against
anthrax, which with' modifications is still successfully
used. The bacillus is called Clostridium chauvei.

The other pathogenic members of this genus are
grouped under the name of gas gangrene* bacilli.
They include the one first found by Pasteur and called
Vibrio septique, the one found by Welch known as B.
welchii and many others.

Studies of them during wars have shown that they
are the chief cause of the gaseous gangrene following
those dirty lacerated wounds so frequent in war, so
rare in peace. These have been called the war wound
bacilli.

Volumes have been written of the investigations of
this group and still there is much confusion in regard
to their relationships. Many names have been used for
the same organism, and many have been the discussions
and refutations in regard to the results published.

Practically it" has been learned from all this study
that such wounds usually contain several varieties of
this kind of microbe, some pathogenic and others merely
harmless companions. It has been shoA\Ti that probably
only six varieties can take part in the process of gas
gangrene. Of course, in these wounds there may be
dangerous streptococci and other microbes as well. All
of these have to be taken Into consideration In the treat-
ment of badly contused, dirty wounds.

A number of the anaerobic bacilli found in these

THE RESISTANT FAMILY 163

wounds during the World War were sho\^^l to be able
to produce a toxin from which antitoxins were pre-
pared, but we know little of the practical appHca-
tion of these antitoxins, for by the time they were ready
to be tested in human beings the war was over. Theo-
retically a polj'^valent antitoxin made from the kinds
of bacilli most frequently found, including the tetanus
antitoxin, should be injected as a prophylactic measure
in cases where wounds of this kind cannot be adequately
treated locally.

CHAPTER XII
THE CLUB-SHAPED GROUP

(Part of the family Mycobacteriaceae)
The diphtheria bacillus clan and relatives.

This is a very large and important group, large enough
and important enough and varied enough to be con-
sidered a family, but it is still only classed under the
term (genus) Corynebacterium, meaning club-shaped
bacterium. The bacilli in different ramifications of the
group, in the different species of the genus, differ in
shape and appearance. Many are club-ended, others
more pointed. Some members have special staining and
other characteristics. These differences distinguish one
strain from another.

The most important member, the diphtheria bacillus,
whose formal name is Corynebacterium diphtheriae,
makes its habitat almost entirely in the human race.
Occasionally it is transmitted from man to an animal.
Thus in a few cases it has been found in pustules on the
teats of cows, and in one case we found it in the throat
of a cat. There has never been a determined hunt made
for it in lower animals, so these may be carriers more
frequently than is suspected. It grows fairly well in
cultures on nutrient jeUies and in broth w^hen kept at
blood temperature, but especially well on blood serum
media.

The diphtheria bacillus has a long record as an

164

THE CLUB-SHAPED GROUP 165

enemy of the human race. It can be traced back over
2000 3'ears in the histories of cases of undoubted diph-
theria. It used to occur in only occasional outbreaks,
but as the population became denser and travel more
frequent, diphtheria began to be continuously present
in the cities, being much worse during some years than
others. People hving in the colder climate grew to fear
it, for it became the most dreaded disease of childhood,
and it also very frequentlj^ attacked grown people.

The diphtheria bacilli have the peculiar function of
producing a strong toxin which is found not in the
germ but in the matter in which it grows. GrowTi in
suitable beef bouillon at blood heat for some days,
Roux, who is now director of the Pasteur Institute in
Paris, found that it made the bouillon toxic. To prove
this, Roux separated the broth from the bacilli by pass-
ing it through a porcelain filter which keeps the bacilli
back. The filtrate contained this very powerful toxin, a
few drops of which sufficed to kill a horse if injected
into its tissues. This, as stated in Chapter III, we call
an exotoxin, since it is excreted into the fluid in which
it is growing and is not contained in the bodies of the
bacilli.

A case of diphtheria develops when one or more of
the bacilli reach a susceptible throat, and having lodged
on the mucous membrane the bacilli multiply and begin
to form their toxin. The toxin acts on the cells of the
mucous membrane, so causing injury and making an
even better soil for the growth of the bacilli. The germs
develop more toxin and this causes more injury. Serum
is exuded, epithelial cells become necrotic, bacteria in-
crease, and thus we have inflammation and the develop-
ment of a gray pseudo-membrane. Some of the toxin

166 WHOS WHO AMONG THE MICROBES

is absorbed into the deeper adjacent tissues and they
become swollen. If the case is a serious one, part of the
toxin passes beyond the tissues involved to the lymph
channels and through them to the blood. Escaping from
the blood capillaries, it passes to all parts of the body.
Then it acts on different parts of the muscular and
nervous systems, resulting in early paralysis of the
heart or of the respiratory center, or later of some of
the voluntary muscles. If the disease affects the laryn-
geal mucous membrane, the inflammatory reaction re-
sults in swelling which causes the loss of voice, then
difficulty in breathing and finally suffocation, unless
rehef is given by inserting a tube into the larynx.

One of the most important pecuharities of the diph-
theria bacillus is that it is frequently found in the
apparently normal throat, and not only lingers there
but multiphes. It behaves somewhat like the typhoid
bacillus in the gall bladder of a typhoid carrier. It thus
remains a parasite in a healthy person and may be
passed to others who are not immune. This is one of the
ways in which cases of diphtheria arise. Here is a
striking example.

Some years ago a nurse attended a group of cases of
diphtheria occurring at a summer resort. On their
recovery she went to take care of a child in a family
li\dng several hundred miles away. Shortly afterward
the only child of the family developed severe laryngeal
diphtheria. One of us attended the case and found
bacilh of the same characteristics in the nurse and the
child. This taught us that a nurse who cares for a csise
of diphtheria should have repeated cultures made
from her throat and not be allowed to go to other chil-
dren until these cultures show no diphtheria bacilli.

THE CLUB-SHAPED GROUP 167

In 1884 the human race first began to make the
acquaintance of the diphtheria bacillus. A German pro-
fessor named Klebs noticed that when a bit of the
pseudo-membrane from a characteristic case was
smeared over a glass slide, stained with methyl blue and
placed under the microscope, it showed a large number
of the club-shaped bacilli and bacilli with more in-
tenseh' stained ends that we have just described. He
found, on the other hand, that when he smeared the
exudate from cases which were probably not diphtheria,
such as cases of inflamed throats in scarlet fever, he
did not see similar bacilli.

The next year another German professor, named
Loeffler, not only confirmed Klebs's work but also iso-
lated the germ, grew it in pure culture and produced
diphtheria in rabbits. Then, as already stated, Roux
discovered that the diphtheria toxin was an extra-
cellular one and that this toxin was the cause of the
throat inflammation, the exudate, the heart failure and
the paralysis of the voluntary muscles. These discov-
eries led to practical applications which have revolu-
tionized our methods of treatment and prevention.

In 1892 one of the \\Titers thought that we could use
our knowledge of the appearance and cultural traits
of the diphtheria bacillus to separate cases of throat
inflammation due to the dangerous diphtheria bacillus
from suspected cases due to the less dangerous strepto-
cocci. This thought led to the development of the first
public health bacteriologic laboratory.

In the sprjng of 1893 the Health Department un-
dertook to make cultures from all suspicious cases and
to isolate only those in whom these bacilli were found.
The cultures were also made to clear cases after con-

168

WHOS WHO AMONG THE MICROBES

valescence. On the twelfth day a swab was gently rubbed
in the crypts of the tonsils and against the nasal mucous
membranes and then stroked over the surface of
coagulated blood serum held in a glass tube. The inocu-
lated culture was then taken to a laboratory and placed
in an incubator at about 97° or 98° F. for ten to twelve
hours. At this time any diphtheria bacilH present would
have increased more rapidly on this especially chosen
medium than the other throat bacteria. A little of the
bacterial growth is then removed from the tube and
spread on a sHde, stained and examined under the high
magnification lens. If any diphtheria-like bacilli are
present they will be discovered, and the person either
has diphtheria or is a carrier of diphtheria or diph-
theria-like bacilli. If there are no diphtheria bacilH in
the culture, the case is probably not one of diphtheria.
The reader notices that these statements are not abso-
lutely positive.

It is now known that in the diphtheria group there
are certain members which have no power to make
diphtheria poison or toxin. These are in every other
respect members of the dreaded diphtheria clan. They
can only be detected by testing them on guinea-pigs,
animals that are very susceptible to the toxic diph-
theria bacilH. If a case does not look hke diphtheria,
we suspect the bacilli may be of the non-poisonous type.
These are called loosely non-virulent diphtheria bacilli.

There are also other bacilli found in the throat of
human beings that resemble diphtheria bacilh in many
respects, but besides making no toxin they make differ-
ent ferments for sugars and are shorter and more regu-
lar in form. These are called the pseudo-diphtheria
bacilli. Their registered name is Corynebacterium

THE CLUB-SHAPED GROUP 169

pseudo-dlphtherlcum. They used to be called Bacillus
hoffmanni, after one of their early introducers. They
are of no kno^^Tl importance except that they may at
first confuse a bacteriologist who is not fully acquainted
with this class and its relations. Other unimportant
relatives are numerous, so a bacteriologist has to be
very well acquainted with them all in order to rule t^em
out as being dangerous if they appear in the culture he
is examining from a case of suspected diphtheria.

Thus, one of the varieties that looks under the micro-
scope very like a true diphtheria produces a yellow
color in its groAvth. This was found for the first time
by some of our Health Department workers long ago
in a sample of cheese that was sent in for examination
because it was suspected of causing some cases of diph-
theria. We soon showed that tliis bacillus, now called
Corynebacterium flavidum, is a frequent habitant of
milk and all of its products and that it is entirely harm-
less for humans.

Then there is that very regularly barred bacillus that
is found so often in the normal linings of the eye and
nose. It goes bj^ the name CorjTiebacterium xerosis and
it too is quite harmless.

There is another variety that may not be so harm-
less which may be mistaken for the diphtheria bacillus
b}' the uninitiated. This is the one that is considered
to be imphcated in that bad ulcer of the throat knoT^Ti
as Vincent's angina. It is an anaerobe and grows so
differently other^-ise from the diphtheria bacillus that
it is considered another genus. It goes by the name
Fusiformis dentium.

If no diphtheria bacilli are present in the throat, the
case is not one of diphtheria and cannot produce diph-

170 WHO S WHO AMONG THE MICROBES

theria. Unfortunately, the absence of the bacilli in a
culture does not absolutely prove these are not in the
throat, since it is possible that the swab did not reach
the exudate or that the culture medium was too dry or
improperly made, so that no growth could develop. The
absence of the bacilli in the culture is considered of
sufficient importance to free suspected cases from isola-
tion, but not to stop the use of antitoxin in any person
who seems to have diphtheria.

The next step in the campaign of the human race
against the diphtheria bacillus was the discovery of
antitoxin. Behring, a German bacteriologist, in 1892
began work upon the possibility of protecting guinea-
pigs against diphtheria, with the hope that if he suc-
ceeded he might obtain something useful for combating
the disease in man. Nearly all the bacteriologists at that
time were trying to find protective substances against
the different poison-forming bacteria. He utilized a
weak solution of iodine to attenuate the living diph-
theria germs and injected these in increasing quantities
into guinea-pigs. After about six weeks to two months
he found that the guinea-pigs had become quite resis-
tant. In trying to discover the cause, he found one day
that the blood of the guinea-pig which had been im-
munized would neutralize the poison of the diphtheria
bacillus which we have already stated was discovered
by Roux. Later he tried giving the toxin itself and
discovered that it stimulated the production of an anti-
toxin in the guinea-pigs. Larger animals were then used
and in 1894 he and Roux gave a paper describing the
beneficial effects of diphtheria antitoxin when given to
those sick with diphtheria. They also believed that it
would be of value in preventing diphtheria.

THE CLUB-SHAPED GROUP 171

In the fall of 1894< we had an opportunity of test-
ing these facts ourselves. In a children's institution
at INIount Vernon a severe attack of diphtheria devel-
oped. Cultures from the cliildren's throats were re-
peatedly made with the endeavor to ehminate all those
who had diphtheria bacilh, but in spite of this the
disease spread. At tliis time Dr. Hermann M. Biggs
came from Europe vriih. a supply of the diphtheria anti-
toxin and we persuaded him to let us use half of his
supply in stamping out diphtheria. We gave the next
morning a small injection of antitoxin to each of the
children and the disease stopped. Twelve da3^s later a
very mild case developed. We again immunized all the
children in the building, and from that time no more
diphtheria developed. Tliis taught us two important
things — that diphtheria antitoxin prevents diphtheria
but also that the prevention is onl}^ for a short time.
This rapid decrease in antitoxin in the body of the
human cases, we learned, was due to the fact that the
diphtheria antitoxin was produced in an animal of a
different species from a human being. We obtain our
antitoxins cliiefly from horses. The horse receives every
two or three da.js, under the skin, an injection of diph-
theria toxin. The amounts are at first small until after
two or three months, when each injection contains
enough to kill a thousand horses, but the horses show
no visible reaction to the injections of the toxin. Be-
cause of the antitoxin then in the horse, it has no effect.
Now it has been learned that when you inject one
species of animal with the blood of another animal, the
foreign blood Is eliminated after a few days.

A little later, we did this very pretty experiment.
Having in the laboratory some antitoxin made In

172 WHO S WHO AMONG THE MICROBES

guinea-pigs and some made in horses, we injected each
of a bunch of guinea-pigs with a Httle of the antitoxin
produced in guinea-pigs and we injected another
bunch with a httle antitoxin produced in horses. The
amount used was what we call ten units. A unit is
approximately the amount of antitoxin which neutral-
izes a hundred fatal doses of toxin for a small guinea-
pig. At the end of two weeks we took a guinea-pig
from each of the two bunches. The guinea-pig that had
received the antitoxin made in its own species showed
no harmful effects from the toxin ; the guinea-pig that
received the antitoxin made in the horse developed an
ulcer where it was injected. The next week another
guinea-pig was taken from each bunch and injected
with two fatal doses of toxin. Again the guinea-pig
which had received guinea-pig antitoxin withstood the
injection without the least damage, while the other
died. Then for seven months we occasionally took
guinea-pigs from the bunch receiving the guinea-pig
antitoxin, and it was not until the end of that time
that they began to be poisoned.

Encouraged by this experience, the Health Depart-
ment of New York City, through its medical inspectors,
treated yearly more than 15,000 children who had been
exposed to diphtheria in their famihes. Of these 15,000
only twenty-five showed any symptoms of diphtheria,
and none of these was severe.

Antitoxin used in the treatment of diphtheria is as
much a preventive as when used to prevent diphtheria.
Its only action is to meet the toxin, combine with it
and neutralize it. A very good analogy is the effect of
water on a fire. Just after a building catches fire a
very little water will put the fire out; a little later

THE CLUB-SHAPED GROUP 173

the extent of the fire will have increased and a part
of the building will be ruined. Still it may be repaired.
If the fire is allowed to burn longer, the building is de-
stroyed and, even though the water extinguishes the
fire utterly, the ^Tecked building cannot be made fit to
live in again. Antitoxin, therefore, must be used in
diphtheria at the earliest possible moment and in a
large enough amount to be sure of neutralizing all the
poison. If used early enough, the disease will surely
terminate in recovery. If used later, the outcome is
doubtful, and there comes a time when it may have
no effect.

With the use of diphtheria cultures to prevent the
dissemination of the bacilli by convalescent carriers
and by healthy persons we were able to reduce in some
measure the number of diphtheria cases. With the use
of diphtheria antitoxin to prevent diphtheria in those
already infected or to cure diphtheria in those having
the disease, a greater reduction in the number of diph-
theria cases and a much greater one in the number of
deaths occurred. In New York City, for instance, the
deaths were reduced to one seventh of what they for-
merly were between the years 1895 and 1915. We
found, however, that many cases were not diagnosed as
having diphtheria until the poisoning had progressed
so far that no antitoxin could remedy it, and that many
undetected cases carrjang diphtheria bacilli scattered
the disease. Not knowing who these persons were, it
was impossible to immunize those whom they could in-
fect. It has already been stated that the horse-made
antitoxin would remain in the human body for only
about two weeks ; it was therefore clearly impossible to
give every child a dose sufficiently often to keep it

174 who's who Among the microbes

immune. We found, then, that in spite of the great
advantages brought by antitoxin, there were in 191 4
in New York City, for instance, still about 15,000 cases
and some 1400 deaths. It became obvious that some-
thing further must be done if we were to eradicate
diphtheria.

We knew that through a substance called toxin-
antitoxin or still another substance called toxoid we
could immunize animals. The first substance was the
toxin modified by antitoxin so that while it would not
be irritating it would still produce immunity when in-
jected into the children. We knew that the toxin acted
upon by formalin, called toxoid, would be changed in a
similar way. We knew that animals receiving these
injections would remain immune for about two and a
half j^ears. We spoke often of using either one of these
mixtures in immunizing children. There were great
practical difficulties, however. We knew that about one
half of the children and four fifths of the adults were
immune in the large cities. These had become so partly
at least through becoming carriers of more or less
attenuated bacilli. How were we to tell which children
needed to be made immune and w^hich children were
already immune.'' The only way available to decide this
was to take a sample of blood from each child and
test it for antitoxin on guinea-pigs. If the children
turned out not to be immune and we tried to immunize
them, we could only estimate our success by again
bleeding them and again testing. Then finally to dis-
cover how long they would remain immune we would
have to bleed them from time to time and test out their
blood on guinea-pigs to estimate our success. This was

THE CLUB-SHAPED GROUP 175

not a practical method of doing the immunization on
a large scale and of studj'ing the results.

A Viennese physician who now Hves in this country,
Dr. Schick, tliought of slightly modifying a test we
had long used in animals and appljdng it in children.
In this test we injected a definite amount of antitoxin
into the body of a guinea-pig. Then we injected into
the skin of this pig small amounts of different cultures
which we suspected were diphtheria bacilli. In another
pig we injected the same cultures but no antitoxin. If
any of these cultures were diphtheria bacilli they would
produce a Httle area of inflammation in the skin of
the pig that had received no antitoxin, but no reaction
in the skin of the pig that had received antitoxin. A
modification of this test was to inject mixtures of toxin
with different amounts of antitoxin into the skin.
Scliick reasoned that if a child had any antitoxin in its
blood it would have it in its tissue fluids ; and the idea
occurred to him that if he injected a very tiny amount
of diphtheria toxin into the skin and the person was
immune, there would be enough antitoxin in the plasma
of the skin to neutraUze it so that no appearance of
poisoning would show itself, while if no antitoxin ex-
isted the toxin would act on the skin cells and a slightly
raised reddened area would appear. Fortunately, tliis
idea proved to be correct and the Schick test became
available. Immediately we saw that in this test we had
an easy method of differentiating the immune from the
non-immune and an easy method of determining how
soon those who were injected became immune and how
long that immunity lasts.

In order to test this out thoroughly we approached

176 WHOS WHO AMONG THE MICROBES

the authorities in charge of a number of children's insti-
tutions, telHng them that we were sure that the test
would do no harm and that the immunizing injections
would benefit the children. We were able to test more
than 10,000 small children. We found the Schick test
in differentiating the immune from the non-immune to
be very rehable. We found that in about four weeks
after receiving the injections some of the children be-
came immune and that most of them became immune
within three months. About 10 per cent, of these young
children required a second series of injections.

We then began to test from year to year to see how
long the immunity persisted. We have continued this
testing for ten years and find that in about 80 per
cent, the immunity has lasted. Those that relapse can
very readily be reimmunized by a second series of in-
jections.

In order to determine fully the value of toxin-anti-
toxin or toxoid injections in practically immunizing
the child population, we and others carefully watched
the results. We tabulated 200,000 school-children,
100,000 of them being untreated and 100,000 being
Schick tested and, if not immune, injected with toxin-
antitoxin. We found that the doctors reported during
the next year more than four times as many cases of
suspected diphtheria among those not tested, and that
all of the severe cases occurred in the untested children.
Some cases were to have been expected, because only
about 80 per cent, of school-children become fully im-
mune from one series of injections.

In small cities hke Auburn, New York, and New
Haven, Connecticut, diphtheria has either been wiped
out or nearly wiped out by the almost general use of

Results from injecting diphtheria toxin intradermally. The
Park test to the left. The Schick test to the right

Dr. Schick making the Schick test — the intradermal test with diph-
theria toxin — on a group of school children

The §175,000 Horse. One of our most famous "antitoxin horses,"
called "Old Faithful" because he produced such high grade
antitoxin for so long a time

THE CLUB-SHAPED GROUP 177

these injections. They can be given in the earliest days
of life, but the best time to give the injections is shortly
after tlJe end of the first and the beginning of the
second year. Babies are found to acquire before birth
immunity from their mothers if they are immune. This
is true for other diseases; that is, a mother who is
immune to scarlet fever or to measles or the many other
diseases, bears an immune baby. As the baby reaches
the age of six months, nine months or a year, the im-
munity lessens or disappears. It would be perfectly
safe to immunize babies at six months of age, but they
are liable to so many illnesses that it seems best to
wait until the baby is at least nine months old, because
many of their ills may be attributed to the toxin-anti-
toxin injections. The easiest time for the public health
agencies to immunize cliildren is while they are at
school, because here they are massed in large numbers.
The objection, of course, is that school-children have
lived to an age when the danger of diphtheria has been
greatly lessened. It does great good, however; in the
first place, it prevents a great deal of mild sickness
from diphtheria. Again, it prevents their taking diph-
theria home to their little brothers and sisters; and,
finally, it educates them and their families as to the
harmlessness of the injections and their value. We must
depend, however, in the long run, on the parents and
physicians seeing to it that the httle children, those of
pre-school age, are immunized.

As we look forward into the future we see the fight
between the human being and the troop of diphtheria
bacilli ending in the conquest of the diphtheria bacilli.
The sooner every child is immunized, the sooner will
tliis be accomphshed.

CHAPTER XIII
THE GROUP OF THE ACID-FAST BACILLI

(Mycobacterium)

Bacilli causing tuberculosis and the "unclean disease/' leprosy
— The glanders bacillus.

The members of this famous group of bacteria are dis-
tinctive in their staining qualities. As their common
name indicates, when once stained — and they are hard
to stain — ^they have the power to retain this stain even
though they are washed with an acid solution which
quickly removes the stain from other bacteria. They
are acid-fast or hold their color or stain tenaciously
against acid. This characteristic of acid-fastness has
grouped them together as a genus (mycobacterium) in
our false-branching family, the same one to which the
diphtheria bacillus group or genus belongs. But they
must be thirty-second cousins if related at all. This
false-branching family is called Mycobacteriaceae,
meaning fungus-like bacteria. Its name indicates the
opinion classifiers have of the close relationship of this
family to the molds.

The head of the group or genus of the acid-fasts is
the dread tubercle bacillus, a germ that has probably
caused more misery, sickness and deaths in civilized
people than any other. It is a thoroughly bad one. In its
wide-spread frequency, its insidious attacks of people
and lower animals under civilization rather than in the

178

THE GROUP OF ACID-FAST BACILLI 179

wilds, its slowly but surely fatal course in a compara-
tively high percentage of the humans it attacks, its
mysterious mode of attack and of its host's counter-
attack, its ability to grow in all tissues producing pro-
tean manifestations of disease — in all of these charac-
teristics it is a microbe worthy of our best efforts to
know it and control its ravages.

Although Villemin had shown in 1865 that tubercu-
lous tissue when ground up and injected into animals
would produce tuberculosis and therefore proved that
the disease was communicable, and that the germ was
in the tuberculous mass, yet many years were to elapse
before the germ was discovered. It was in 1882 that
Robert Koch solved the myster}^ Staining methods had
greatly improved since Villemin's time and Koch took
advantage of these changes. He found that if he
smeared a drop of sputum on a glass slide, dried it in
the air, then passed it through a flame sufficient to
coagulate the albumin and fix it fast to the glass,
placing this in an almost boiling solution of fuchsin and
carbolic acid (phenol), everything on the slide was
deepl}'^ stained. Then he made his discovery. He im-
mersed this slide in a bath of alcohol and dilute hydro-
chloric acid and washed out all \asible color. When he
placed the slide under a highly magnifying lens he was
surprised and dehghted to see httle bright red rods.
These were the tubercle bacilli, which, as we said, are
hard to stain and equally hard to decolorize. This stain-
ing method is made use of in helping to detect these
bacilli in sputum or in other secretions or tissues of the
infected host.

Koch was also successful in cultivating the tubercle
bacillus. He removed aseptically a piece of tuberculous

180 WHO 8 WHO AMONG THE MICROBES

tissue and planted it on coagulated blood serum. After
a number of days little gray colonies developed on the
surface which gradually became thick and wrinkled.
When these bacilli were examined chemically it was
found that they contained a large amount of wax-like
substance. This it was that interfered with the staining
by ordinary methods and made it difficult to decolorize
them after they were stained. When these bacilli from
the culture were injected into animals they developed
tuberculosis. This isolation of the tubercle bacilli by
Koch was one of the most important discoveries ever
made. It became possible to attack the disease far more
intelligently.

When Koch discovered the tubercle bacillus in
tubercles not only in tuberculosis in man but also in
that of birds and cattle, he at first thought that the
bacilli were the same in all animals. After further study,
he and others were able to prove that the tubercle
bacillus of birds was chiefly dangerous to birds ; that
it occasionally infected pigs and possibly human beings,
but the latter were rarely if ever attacked by the bird
strain or type of tubercle bacilli. For a time it was
still thought that the tubercle bacilli which attack
human beings and cattle were alike. Further study by
Theobald Smith, one of the best known of American
bacteriologists, discovered certain differences between
the tubercle bacillus obtained from a cow and the
tubercle bacilli obtained from a human. Robert Koch
then tested the type of bacilli found in adult human
beings. He discovered only the human type and gave
it as his opinion that the bovine type was of little or
no importance in man. This opinion was not accepted
by all and a series of investigations were started in

THE GROUP OF ACID-FAST BACILLI 181

England, in Germany and in the city of New York. This
last investigation was carried on in our laboratory.
Fortunately, these three groups of investigators came
to the same conclusion. They agreed on the fact that
the bovine tubercle bacilH were the only type of bacilli
that infected cattle. This type was, however, more
widely distributed, for it was found that it also in-
fected hogs and, most important of all, it infected in-
fants and children. It was found that infants and very
young cliildren developed general tuberculosis when
infected with the bovine bacilH, and this took place al-
most as readily as from the human bacilli. It was al-
most always fatal. Older children developed only local
tuberculosis such as in the lymph glands of the neck.
Adults, as Koch had earlier found, were free from
bovine infection. The outcome of the investigations,
therefore, was that practically all human tuberculosis
after the age of cliildhood was due to bacilli of the
human type. A controversy then arose as to whether
the absence of the bo\'ine type in adults was due to
the fact that original infection was with human bacilli
or that the bovine bacilli had caused latent infection
in childhood but because of remaining in the human
body so long had gradually adapted themselves to the
human tissues and taken on the characteristics of ba-
cilli of the human type. It had already been noted that
the majority of children in cities become infected be-
fore the age of puberty, and that much of adult tuber-
culosis was due to the breaking out of this arrested
focus.

Careful study of material in which the bovine bacilli
had remained in human tissues for three or four years,
and of human bacilli which had remained in cattle for

182 WHOS WHO AMONG THE MICROBES

at least one or two years, showed no changes in the
two types during their stay in human beings or cattle,
so we believe that although conceivably under peculiar
conditions there may be an occasional slight change in
the types of bacilh, yet practically all human tuber-
culosis of adult life is due to an original infection with
the human type from a human case and has no relation
to milk or any other food product.

Let us now go on to another aspect of tuberculosis.
Many years ago a young man, who became one of the
best beloved American physicians. Dr. E. L. Trudeau,
discovered that he had tuberculosis. He had just fin-
ished his hospital work as interne and was married and
ready to start on his practice. He did not feel as well
as he thought he should and, seeking an examination,
found that he had tuberculosis. At that time, for some
reason, tuberculosis was an even more serious disease
than it is at present. The conditions found in his chest
on a physical examination seemed to condemn him to
an early death if he remained in the city. After con-
sultation with some of his best medical friends, he de-
cided that his only chance was to leave New York and
go up into the North Woods, where in the clean em-
bracing air he could strive to so build up his resistance
that the germs of tuberculosis would fail to progress.
Although he never became completely well, his disease
became arrested. He decided to try and help other con-
sumptives to achieve equally good results. In order to
bring home to others the value of good air, rest and
good food in increasing resistance to the invasion of
the tubercle bacilli, he planned the following experi-
ment:

He selected a number of rabbits for the demonstra-

THE GROUP OF ACID-FAST BACILLI 183

tion. He injected each of them with a similar amount
of tubercle bacilli. Some of the animals he placed in
the cellar, which was fairly light but not especially
well ventilated. The others he placed in a well-sheltered
porch where they were in access to the sunshine and the
fresh air. To the first lot he gave the ordinary rabbit
food ration ; to the second lot he gave a special diet,
selecting for them the food which they most desired
and was best for them. The rabbits living in the cellar
all developed fatal tuberculosis. The rabbits Hving
under the best conditions, with access to the open air
and the sunshine, recovered without any signs of per-
manent infection. Since then all the world has come
to realize that while probably every member of the
human race living in crowded communities is liable to
infection from tubercle bacillus, yet we can so increase
our resistance that the bacillus is barely able to Hve
in our tissues, and if it does, it is usually utterly un-
able to cause progressive disease. Wliile, therefore, we
have not been able to find any cure for tuberculosis
and, until recently at least, no vaccine or chemical
substance which gives hope of making us immune, yet
we have, through increasing the general resistance of
the people and often isolating those with open tuber-
culosis, been able to conquer the disease to such an
extent that less than one quarter of the number of
people die from tuberculosis as did fifty years ago.

So far as cattle are concerned, the question of tuber-
culosis is almost as important for them as human tuber-
culosis is for us, and as we depend on cattle for meat
and for milk, anytliing which endangers their health
is of great importance to us. We have with cattle the
ability to handle the matter of infection in a way which

184 WHO S WHO AMONG THE MICROBES

we cannot do with human beings. We can eliminate
from our herds all those that are susceptible. This
brings us to the study of a toxic product made by these
baciUi which we call tubercuhn.

Koch in 1889 discovered that in the tubercle bacilli
themselves, and in the fluid in which they had grown,
a specific toxic substance developed which, when given
to tuberculous patients, caused a marked general re-
action and also a local one of the tissues infected.
There was a rise of temperature and an increase of
signs of inflammation in the infected area. He found
that when the beginning dose was very small he could
avoid any apparent reaction, and that by gradually
increasing the dose the people injected would become
less and less susceptible. He hoped, therefore, that he
had a vaccine which would increase the resistance to
the invasion of the bacilH and so help recovery. Those
of us who were alive at that time remember how in
1890 a great excitement spread among those who had
tuberculosis. They all longed to try this new vaccine
which was to cure them. They sacrificed everything to
get to Berlin and take the supposed cure. It finally
developed that the immunizing effect was very sHght
and only of value in incipient cases. In fact, unless the
tubercuhn could be used with the greatest care it pro-
duced far more harm than good. Something of great
value, however, had been determined — namely, that
the injection of even tiny amounts of tuberculin caused
a specific reaction which could be utilized to detect the
earhest stages of infection in both human beings and
cattle. This is given in different ways. If a small amount
is injected into the skin it causes in any person or ani-
mal that has any tuberculous tissue a local redness and

THE GROUP OF ACID-FAST BACILLI 185

swelling. A similar effect follows placing a drop of a
dilute solution on the mucous membrane of the eyelid.
If we have a taint of tuberculosis in our body the
mucous membrane becomes inflamed. The skin reaction
is absolutely harmless. If, however, we wish to be cer-
tain whether or not an animal has tuberculosis, we
use a subcutaneous injection ^dth a larger amount.
After about six hours the temperature begins to rise,
and hour by hour over a period of eight or ten hours
it rises and then falls. Such animals are known to be
tuberculous. They are removed from the herd, slaugh-
tered, and if markedly tuberculous they are put in the
rendering tank and the various chemical substances in
their bodies separated and used for various commercial
products. If only a tiny amount of material such as a
Ij^mph gland is tuberculous and this can be entirely
removed, they are used for food. The farmer is reim-
bursed by the State or the Federal Government for the
full amount of money which the cow was worth. In this
way millions of dollars have been spent to eUminate
tuberculosis.

In spite of no worth-while success, the effort to pro-
duce a vaccine has been continued down to the present
day, and at the moment we are using with some hope
of success a vaccine developed by Calmette, who is the
assistant director of the Pasteur Institute in Paris.
For years he has been attempting to immunize animals
with attenuated living tubercle bacilH. After having
tested monkej's and calves and rabbits, he began five
years ago to give it to infants ; at first to those born of
tuberculous mothers, then to those born in tuberculous
famihes and now to all infants. His method is to give
the baby during the first ten days of life three feedings,

186 WHO S WHO AMONG THE MICROBES

each of which contains about a half bilhon attenuated
bacilli. The baby shows no apparent ill effect. This
vaccine has been given to over 100,000 infants in
France alone. He believes that the results give proof
that the vaccine has immunized the great majority of
them. The death-rate of untreated infants from tuber-
culosis during the first year of hfe in tuberculous fam-
ilies in France is about 20 per cent., while in those
receiving the attenuated bacilli it is only 1 per cent.
Our laboratory has been trying it out through one of
our co-workers, Dr. Camille Kereszturi. She, with two
devoted nurses, has during the past two years fed the
vaccine to over 150 infants. Only two of these have died
of tuberculosis. The first one was a premature baby,
that died in its third month. This was undoubtedly a
case of congenital tuberculosis. Its mother died from
generaHzed tuberculosis at the time of giving birth to
her child. The other was a fine child which was per-
fectly well until it was five months of age. Then it
developed whooping-cough and soon afterward signs
of tuberculosis. The disease progressed to a fatal ter-
mination. Tliis child was not separated from its mother
for the first month, contrary to Calmette's advice, so as
to give time for the development of immunity from the
vaccine. Both its parents had tuberculosis. The sputum
of the mother contained many bacilli. All the H^^ng
babies are well. The enthusiasm of the French leads us
to hope that Calmette is right. We are only certain the
vaccine is harmless, and we are looking forward with
great interest to watching for the next year or two the
results of the treatment. Subcutaneous injections are
now being used. These seem to be harmless and are more
effective.

THE GROUP OF ACID-FAST BACILLI 187

An important relative of the tubercle bacillus is
the leprosy bacillus or Mycobacterium leprae. This
acid-fast non-motile Httle irregular rod, very like the
tubercle bacillus, probably never has killed anything
like the number of people that the tubercle bacillus has,
but the terrible nature of the disease it causes has made
its activities dreaded almost as much, perhaps more
in earher times. Through ancient literature are many
accounts of the pitiable condition of those afflicted with
it. The fear of infection made them outcasts. "Unclean !
Unclean !" they were compelled to cry if any one ap-
proached them.

It is interesting that it was probably in connection
with leprosy, which is not highly contagious, that the
first ideas of infection became implanted, and that strict
laws of segregation such as those given in Leviticus
were promulgated. No doubt other diseases with skin
manifestations were included in those times under the
term "the unclean disease." The enforced isolation of
this type of disease led to a marked diminution of
cases in those areas, and now in many countries of the
world leprosy has practically disappeared.

It is estimated that there are now only about two
or three million cases in the whole world, of which the
United States has about a thousand.

We get a brilliant picture of the microbe if we
stain a spread of infected tissues by the method used
to detect acid-fast bacteria. Blue-colored tissue cells are
filled with the brilliantl}' stained red rods.

And yet the question of how to grow these leprosy
bacilh is still not definitely solved. We are not even
sure that a true leprosy bacillus has been cultivated.
The reason we can't be sure is because the lower ani-

188 WHOS WHO AMONG THE MICROBES

mals are not clearly susceptible to this disease and
we have no specific test to indicate that we have the
right culture. A number of kinds of partially acid-
fast cultures have been isolated, and some workers have
claimed that they can produce leprosy in monkeys with
them by repeated doses. There is no satisfactory cura-
tive treatment for leprosy.

As with all other groups of microbes there are a
number of harmless unimportant relatives of these
harmful acid-fast bacteria. They derive their interest
chiefly from the fact that they might on occasion be
confused with the harmful ones. Thus there are certain
forms that grow on grasses and so may get into butter,
milk and cheese. Then there are forms found in cold-
blooded animals that do not seem to be at all harmful
for man, in certain fish, snakes and turtles. A culture
obtained from turtles is one that was used by the Ger-
man Friedman to make a vaccine that he claimed would
cure human tuberculosis. Like many similar claims for
other so-called remedies, it proved to be ineffective.

A very distant relative of the tubercle bacillus is the
glanders bacillus discovered by Loeffler in 1882. It be-
longs in the "false-branching" family but is not in the
acid-fast group, so it is considered as belonging to a
distinct genus and is given the specific name Pfeifferella
mallei. It causes a well-known and earher rather com-
mon disease of horses, asses and mules, characterized
by the formation of small nodules chiefly in skin and
mucous membranes that may ulcerate. This disease is
known as glanders, or farcy. It may be transmitted to
man and cause his death. Now, with the substitution
of horses by the automobile in cities, and with the ehm-
ination of the common drinking-fountain, glanders has

THE GEOUP OF ACID-FAST BACILLI 189

practically disappeared. This microbe is like the
tubercle bacillus in its ability to produce a substance
similar to tuberculin called mallein. It gives a reaction
in animals affected with glanders comparable to the
reaction of tuberculin in animals affected with tuber-
culosis. Injections of it are used to detect hidden glan-
ders. While the disease is now infrequent, we should be
on our guard against it in any places where many
horses are kept.

CHAPTER XIV
THE COMMA FAMH^Y AND CHOLERA

(Spirillaceae)

In the early nineties the words Asiatic cholera were
still causing thrills of dread, especially in the minds
of those who were traveling to Europe. For at that
time the last great epidemic of this terrible scourge
was still raging, and a devastating and, at first, un-
explainable outbreak had just occurred (1892) at
Hamburg. This whole epidemic extended over a dozen
years. At its beginning, 1883, in order to investigate
its cause a cholera expedition headed by Koch was sent
to Egypt, where the disease had broken out in force.

Long before this time water was suspected of being
the chief medium for conveying the cholera "virus" to
man in epidemic form. Indeed, as early as 1854 Snow
of England practically proved that cholera followed
the drinking of water that was exposed to the dejecta
of cholera patients. Many agreed with him that cholera
was a specific infection due to a special virus, but
others still thought that a group of general conditions
was necessary to produce an epidemic. Indeed, even
after the discovery of Koch's comma bacillus, authori-
ties such as von Pettenkofer and his followers believed
that the receding of the ground water in a locality
was essential to the breaking out of an epidemic.

At this time, when our knowledge of microbes was

190

THE COMMA FAMILY AND CHOLERA 191

still in its infancy, there were many other mistaken
ideas that different people had of the conditions, in-
cluding that of the hand of God, which they thought
caused or helped the outbreaks of cholera and other
scourges.

Among them was the idea, held until very recently
of most communicable diseases, that the air about the
patient contained an effluvium given off from the pa-
tient that caused the disease if one breathed it in. A
description of the results of the brutal and dangerous
custom of allowing people to die uncared for and alone
because of this idea would fill many a chapter of his-
tory of the world's sorrows.

It is chiefly the work of Snow and his Hke, who
were true logical observers, that made a change for
the better, as I said, long before the final proof came.

Snow insisted that the characteristic rice-water stools
of the cholera patients were the chief, if not the only,
site of the cholera poison, and that these discharges
reaching the drinking-water constituted the chief means
of the spread of an epidemic. Of course, he recognized
that there might be other ways also for the poison to
be communicated.

Newsholme ^ calls attention to an absurd (to us now)
incident that occurred in Scotland at the time the
Broad Street pump epidemic started. He states:

"In 1853, when cholera, which had previously dev-
astated Great Britain, was once more threatened, the
Presbytery of Edinburgh wrote to Lord Palmerston,
then Home Secretary, suggesting that 'in the circum-
stances a national fast should be appointed on royal

^ "Evolution of Preventive Medicine," The Williams & Wilklns Co.,
Baltimore, 1927, p. 10.

192 WHO S WHO AMONG THE MICROBES

authority.' In his answer the Home Secretary made a
statement which shows the reahzation of the fact that
epidemics are governed by natural laws. He wrote:
'The weal or woe of mankind depends upon the observ-
ance or neglect of these laws.' "

He further emphasized that activity in the direction
of purification of towns was preferable to humihation,
adding :

"The best course which the people of this country
can pursue to deserve that the further progress of the
cholera should be stayed will be to employ the interval
that will elapse between the present time and the be-
ginning of next spring in planning and executing meas-
ures by which those portions of their towns which are
inhabited by the poorer classes, and which from the
nature of things must most need purification and im-
provement, may be freed from those causes and sources
of contagion which, if they be allowed to remain, will
probably breed pestilence, and be fruitful in death in
spite of the prayers and fastings of a united but
inactive people."

In St. James parish, where the famous Broad Street
pump was situated, 700 people died of cholera within
seventeen weeks. Snow, who had long thought that
infected water was the cause of cholera, called attention
to the fact that the great majority of these cases oc-
curred within the area supplied with water from this
pump. Few records were kept in those days, and the
people were ignorant of health makers and non-observ-
ant, so Snow had great difficulty in getting clear-cut
information ; but he persisted in his investigations, even
giving up his practice for a while in order to have
time to visit personally the families in wliich cholera

Protecting an infant from tuberculosis. The doctor having put the
required amount of the Calmette vaccine into the milk is going
to feed it to the baby.

THE COMMA FAMILY AND CHOLERA 19S

had occurred. In his search he unearthed a number of
significant incidents which together formed an impres-
sive mass of evidence in favor of the town pump of
Broad Street being infected with cholera virus. One
or two may be cited : ^

There were many town pumps at that time, but ac-
cording to Snow the Broad Street pump seemed to be
a favorite one. One woman who hved at a distance from
the pump had a cartman bring the bottles of water
from this well occasionally, because she thought it so
good. Just at the time that the epidemic broke out he
had brought her some. A niece, hving in an area where
they had no cholera, was 'sdsiting her when the water
arrived, and they both drank of it freely. Within two
days they each came doTvn with a fatal attack of
cholera.

A man Hving near the pump and using its waters
was stricken with the cholera. He sent for his brother,
who Hved in a non-cholera district. The brother arrived
after the death of the man and was not allowed to see
the body. He drank some of the water, however, be-
fore he left for home. That night he came down with
cholera and quickly died. No other cases of cholera
developed in that place.

Snow showed further that while a certain factory in
the neighborhood that had a well of its own had no
cases of cholera, another near-by that kept two tubes
of drinking water dra\^Ti from the Broad Street well
had many cases of cholera.

Snow examined the surroundings of the Broad Street
well and found a deplorable condition. From a near-by

* See Rosenau's very good description of the epidemic in his "Pre-
ventive Medicine and Hygiene," 1927. New York: D. Appleton & Co.

194 WHO S WHO AMONG THE MICROBES

house went a defective drain to the sewer, passing the
well within three feet. Near the well also was a cesspool,
over which was a privy used by people of this same
house. In this house there must have been an earlier
unrecognized case of cholera. Later four cases of
cholera developed there.

When the Broad Street well was demohshed the cases
of cholera in that neighborhood ceased.

Notwithstanding Snow's striking array of evidence,
proof of the important part played by water in out-
breaks of cholera had to wait until some time after the
discovery of the little curved baciUus, comma shaped,
that Koch first found in the dejecta of cholera patients
in Egypt.

When Koch saw under the microscope myriads of
minute curved germs and scattered spirals mo\4ng rap-
idly to and fro with vibrating motion in the fluids ob-
tained from the stools of cholera patients, and when
he could not find similar ones in normal stools or in
those from other diseases, he was sure that these tiny
\^agglers were the cause of cholera, though he hadn't
yet obtained a pure culture of them. He said, "Send me
to India, the home of cholera, and I will prove to you
whether or not these are the microbes that are doing the
mischief." So he was sent to India. There he found the
same kind of a germ in the cholera cases and did not
find them in others. He also found them in a stagnant
tank of water which people coming down with cholera
were drinking. And better yet, he obtained a pure
culture of the micro-organism. He called this the comma
bacillus or the comma vibrio. It was also called the
cholera spirillum. It is in every sense of the word the

THE COMMA FAMILY AND CHOLERA 195

chief of the group of microbes composing the family
of spirilla or conmia-shaped germs.

Koch had great difficulty at first in completing the
chain of e\'idence that would prove his contention that
the microbe he found causes cholera. This was because
the organisms, though growing so abundantly in the
human intestinal canal, could not be made to produce
symptoms like cholera in any of the lower animals or
even give evidence of growing in their intestinal canals.
He found later that the cholera vibrio does not Hke
acid even in traces. In fact, it has been found that they
are quickly destroyed by weak acids. It was then sus-
pected that when animals were made to swallow them
the acid in the gastric juice killed them before they
could reach the intestines. After Koch found this out, he
succeeded in producing symptoms and intestinal lesions
in guinea-pigs similar to those in many humans by
introducing large amounts of the cultures through the
mouth by catheter after first neutrahzing the stomach
contents with a solution of bicarbonate of soda and
inhibiting peristalsis of the intestines by the use of
opium.

In the meantime, one of the earliest accidental in-
fections of laboratory workers furnished more satis-
factory if more tragic e\'idence that the cholera vibrio
is able to produce cholera in man.

In 1884) a student studying the cholera germs in
Koch's laboratory in BerHn became acutely ill with a
typical attack of cholera. At that time there were no
cases of cholera in G^^rmany. The organisms were found
In his rice-water stools.

It seemed as if the vibrios were able to pass the gas-

196 WHO S WHO AMONG THE MICKOBES

trie juice guard of man more readily than that of most
of the lower animals. Man is probably also much more
susceptible to infection than animals. Having once
passed that guard, Koch claimed they were usually
able to multiply exceedingly in the alkaline medium of
the intestinal contents, which suited them very well.

It was shown later that Koch was right. When a few
pass the stomach into the intestines they soon may over-
grow the normal inhabitants of the intestines, especially
in those people who are suffering from indigestion. In
their growth they produce a toxic substance that makes
the intestinal wall red, swollen and hemorrhagic. They
cause their victim to have violent vomiting and diarrhea
which take away so much fluid from his body that the
patient may quickly look like a wrinkled old creature —
a veritable mummy. If saline infusions are given at this
stage the patient's change back to a normal appearance
may be remarkable. But alas ! in at least one half the
cases this change is not lasting. In these cases the diar-
rhea and vomiting continue, the patient passes into a
collapse and quickly dies. The comma vibrios are found
in almost pure cultures in the characteristic rice-water
stools of these cases.

Koch's inability to demonstrate clearly and quickly
a chain of evidence proving the etiologic relationship of
the cholera vibrios to cholera allowed the doubt to grow
in many people's minds as to the specific nature of the
vibrio in its relation to cholera.

Two men who were among the unbelievers said they
knew they could swallow masses of cholera vibrios with-
out developing cholera afterward. So, having first
taken some sodium bicarbonate to neutralize the acid
in their stomachs, and some opium to stop the peristal-

THE COMMA FAoSIILY AND CHOLERA 197

sis of their intestines and keep the organisms from be-
ing hurried through, they each swallowed about a tea-
spoonful of a fresh vigorous broth culture of the vibrios.
Von Pettenkofer, of the ground-water theory of cholera
epidemics, was one of these men. Within a day or two he
came down with a severe attack of diarrhea from which
he recovered in a few days. His companion, during the
night following the injection, became very ill, he had
severe diarrhea, cramps and vomiting, with great pros-
tration. His stools became typically rice-water. This
condition lasted several days. Then he gradually re-
covered. Clinically he had had a typical attack of
cholera. The cholera "vdbrio was recovered from the
stools of each man.

Other laboratory workers repeated this experiment,
using themselves as the test animals — some came down
with typical cholera and some did not. The fact that
some did not was explained by the assumption that
these had a higher degree of resistance than others.
Then another student, working in Hamburg with cul-
tures, came down with the disease and died.

On the whole, these human experiments and the
accidental infections made the evidence so strong that
the case for the cholera vibrio being the specific crim-
inal in cholera epidemics was considered won, at least
by the majority of research workers.

Then came the crowning evidence. This was gath-
ered during the fatal outbreak of the disease in Ham-
burg in 1892. The clear-cut results from the investi-
gation of this evidence form one of the most instructive
and convincing demonstrations we have ever had of the
relation between the dejecta of cholera patients, the
cholera \dbrio and the water supply 'with its control.

198 WHO S WHO AMONG THE MICROBES

It was during the time the great epidemic referred
to at the beginning of this chapter was nearing its end
that this tragic outbreak occurred.

Cholera smolders in Asia chiefly along the Ganges
and in Lower Burma. Why it remains endemic, form-
ing hotbeds in certain areas, no one clearly knows. Per-
haps there are more chronic carriers in these areas than
investigators have been able to demonstrate.

This last world-wide outbreak was said to have been
started after a great festival along the river Ganges,
in whose waters many people bathed as a part of the
rites.

As the epidemic spread over the continents it mani-
fested itself with marked intensity in Russia. It is
estimated that in Russia alone, during the dozen years
these outbreaks continued to occur, the vicious little
comma vibrio claimed over 800,000 victims.

It was to be expected that an epidemic might spread
with great vigor in countries hke Russia, because of
the wide areas not under hygienic control. But in those
parts of the world that were able to carry out rules
of hygiene it was taken for granted by the beginning of
the nineties that enough was known about cholera to
prevent its spread in such areas.

They knew the cholera germ was in the dejecta of
patients. They knew that this germ might be carried
by the water as well as by direct contact. They knew,
or thought they knew, that if the dejecta of patients
were disinfected, cholera would not spread.

And then came the sharp Hamburg outbreak. The
authorities were filled with consternation. They
couldn't understand it. That such a thing should

THE COMMA FAMILY AND CHOLEKA 199

happen in such a well-conducted place in one of the
headquarters of culture and hygienic eflBciency!

From the middle of August to the middle of October
1892 there developed about 17,000 cases. Death fol-
lowed death — fully half of the cases were fatal. In
the near-by city of Altona there were scarcely any
cases.

Investigation brought to Hght the deplorable fact
that while Altona was using filtered water from the
river Elbe, Hamburg was using the raw unfiltered
water from the same river.

Further search showed that the epidemic was prac-
tically confined to those using this unfiltered water.

But they cried, "How did the water become in-
fected.'' There w^re no cases of cholera along the Elbe
just before the outbreak." That the water was infected
was proved by Koch's finding the comma vibrio in it.
Then they found the probable source of the outbreak
among a number of Russian immigrants from infected
areas, waiting in barracks along the Elbe to be shipped
to the United States.

The authorities didn't find any pronounced cases of
cholera among them when examined, but they decided
that there must have been some undetected light cases
or recent convalescents. At that time it had not been
determined that healthy people might carry the germs.
No doubt there were several of the different types of
carriers among these Russians, and they constituted
the first source of the pollution of the Elbe. Then, as
other cases came dowTi, all emptying their sewage into
the Elbe, the outbreak grew in intensity.

When the inhabitants began to boil their water, and

200 WHO S WHO AMONG THE MICROBES

when they established an efficient filtering plant for
the river water, the outbreak stopped.

This epidemic might almost be called a pandemic.
It has been called so by some ; for a few cases, at least,
appeared in almost every country in the world. In the
United States there were several cases, but owing to
the vigorous inspection and quarantine of incoming
steamers, and to the fact that no water supply became
infected, the disease did not assume epidemic pro-
portions in this country.

An interesting incident occurred in New York City
at that time in connection with the outbreak of cholera.

Dr. Dunham, who was one of our noted pathologists
and who was the first American to study cholera, late
one night performed an autopsy on a case of cholera
that had died at the isolation hospital of New York
City. He gave his trusted helper Toby some of the
autopsy material in a sealed pail to carry to his labora-
tory in the Bellevue Hospital Medical College. As Toby
was hurrying from the morgue to the laboratory
through the notorious "gas-house" district he almost
collided with a policeman coming suddenly around a
comer. "Hi! Where do you think you are going?"
called the officer, seizing him by the arm. "Look out,"
said the messenger. "Don't disturb this pail." "What
have you got in it.'^" asked the officer. The messenger,
who was something of a wag, replied solemnly, "I can't
tell you." "You must show it to me^" insisted the of-
ficer. "I cannot open it. Don't you see it is sealed.'^"
said the messenger, pointing to the sealing labels plas-
tered over it. "Well, then, you'll have to come with me
to the station-house. We'll see if the chief can make
you talk." It was too late to confess now, even if the

THE COMMA FA^IILY AND CHOLERA 201

messenger had thought it wise to do it. So he went with
the officer to the near-by station-house. When the mes-
senger told the captain what he had in his pail, every
one gasped with fear and horror of infection, and the
police captain hurriedly detailed a squad of policemen
to escort the messenger with this dangerous package
safely to the laboratory.

It was during this investigation of cholera at this
time that Dr. Dunham de^dsed the famous solution that
bears his name — Dunham's peptone solution. The
cholera microbes develop in tliis medium the cholera red
reaction. He showed that while the cholera red re-
action was not absolutely specific for the cholera vibrio,
all true cholera strains show it. So any strain not show-
ing it is not a cholera vibrio. Tliis reaction was one of
the many finds that were thought to be peculiar to the
cholera \abrio, but that later researches showed not to
be absolutely distinctive, but still of great practical
value.

During the search for cholera vibrios a discovery
was made similar to that which has been found in
connection with all well-studied microbes ; and, as al-
ways, especially in the early days of investigation
among microbes, led at first to open the doubt then
existing in the minds of the few as to the specificity of
the microbe in question.

This discovery was the existence in conditions other
than cholera of vibrios so similar to the comma vibrios
that in most instances special tests had to be developed
to show that they were not identical Tv^th the cholera
vibrio.

Thus, similar vibrios were occasionally found in nor-
mal saHva, others in a certain kind of cheese; others,

202 WHO S WHO AMONG THE MICROBES

and many others — for vibrios like water — found in
water. Then some were found in the diarrheal stools
of infants and adults. So there was finally a fair-sized
family of vibrios to be studied and shown up as being
composed of distinct individuals.

Many were the points of difference and resemblance
between these forms, brought out by the painstaking
studies made of them, but little emphasis is laid now
on most of these points so strongly insisted upon by
their discoverers at that time. For the so-called sero-
logic tests proved to be so specific that the others were
found to be for the most part unnecessary. Of course,
selective culture media must be used to get the strains
easily in pure cultures. Dunham's alkaline peptone
water is favorable for growth, and as these vibrios grow
more abundantly in the presence of oxygen, they may
be found in a short time in large numbers at the top
of the medium. A small loopful taken from the upper
part of this growth after six hours and planted on
plates of nutrient alkaline agar medium to which a
httle white of egg has been added will show very typical
colonies of the comma vibrio, which may be fished and
planted on plain agar and fished again before we can
be sure we have a pure culture. There have been many
other methods recommended for obtaining pure cul-
tures of the cholera vibrio.

Then when we are -sure we have a pure culture we
test it by employing the serologic test that is now
always used to determine the relationship of identity
between strains — namely, the absorption of agglu-
tinins.

By this test it has been shown that the real cholera
vibrio is rarely found except in cases having typical

THE COMMA FA3IILY AND CHOLERA 203

symptoms of cholera. In the presence of an epidemic
or in countries where it is endemic it may be found in
less typical cases and in an occasional normal person.

Another specific test that was earlj^ brought out by
Pfeiffer may also be used, but it is more cumbersome
and it is not as clear-cut as the agglutination test. This
is the so-called Pfeiffer's phenomenon or the bacteri-
cidal test, which we have already' described. This test
was sho^Ti for the first time in connection with studies
on the cholera vibrio.

Pfeiffer found that the serum of animals that had
been immunized against cholera contained a substance
that together with the peritoneal fluid would kill and
then dissolve the cholera spirilla when mixed with them.
Such a serum had ver}" little if any effect in curing the
cases, but it might prevent the disease if given before
the infection.

This led investigators to try preventive vaccines in
face of an epidemic and in those countries where the
disease is endemic. As a result they have found that a
vaccine does have marked protective action in a large
percentage of the cases. It is of almost as much value
as the typhoid vaccine against typhoid fever. Any one
about to visit a country where cholera is endemic should
take this vaccine.

CHAPTER XV
THE COILED-HAIR FAMH^Y

(Spirochetacese)

The pale spirochete and the immoral disease — Spirochetes in
relapsing fever and in yellow fever.

As long ago as 1833 a German named Ehrenberg,
while examining some water under the microscope, saw
a number of squirming creatures that looked Hke living
motile coils of hair. Because of this appearance he
called them spirochetes. Since that time many similar
germs have been discovered, some in stagnant or fresh
water, in the sea, and one variety even in hot springs ;
some growing as harmless parasites in animals, others
invading their hosts as deadly enemies. No known
spirochete has so far given evidence of being useful to
man.

Among the known harmful microbes, perhaps the one
that has done the most all-around damage to human
beings, from the disturbing of domestic life to the ulti-
mate killing of its victims, is the chief poisoner of this
group, called familiarly by the unassuming name, the
pale spirochete.

According to the custom of classifiers, its scientific
name, which was Spirocheta pallida, has been changed
to Treponema pallidum. The reason for making this
change is the usual one. The classifiers decided that this
spirochete had characteristics so different from those

204

THE COILED-HAIR FAMILY 205

of the then knowTi spirochetes that a new genus should
be created for it. They reported their claim and gave
their genus the name Spironema. Finding that this
name had been preempted for a class of mollusks, they
chose the name Treponema, which means a turned or
turning thread.

And so the pale spirochete, or pale turned thread,
at present must be introduced formally as Treponema
palhdum, the chief of its genus. This arch criminal,
even more than other varieties that have been placed
in its group, is made up of extremely delicate translu-
cent material. For this reason it remained hidden from
the searching eye of the microscopist until only a com-
paratively few years ago.

Though it insinuates its way into nearly all of the
tissues of those unfortunates who have become infected
with it, even crowding their lymph nodes, livers, spleens
and other parts of the body at certain stages of the
terrible protean venereal disease that it causes, yet it
was missed completely by all of the bacteriologists who
had been eagerly hunting for the cause of syphihs, as
the disease it causes is called, ever since microbes were
discovered and microscopes were perfected.

"The history of the search for the cause of syphilis
is a tale to make the judicious grieve," says Osier, ^
One hundred and twenty-five claims made in the twenty-
five years before 1905, each of a different cause, are
quoted by Lasson.

Finally, in 1905, two biologists, Schaudinn and

Hoffmann, who had made protozoa their special study,

began to investigate the cause of syphihs. Soon they

found sometliing that filled them with hope. In ma-

* Osier, "Modem Medicine," 1907, vol. iii, p. 440.

206 WHO 8 WHO AMONG THE MICROBES

terial scraped from a primary mucous sore on the lip
of one of the men under examination they saw through
their immersion lens some extremely delicate spirals
that occasionally made a sHght jerking motion.

"Here is a new microbe," said one of the observers.
"They may be only tissue fibrils," said the other. "No,
that can't be," said the first; "that is the motion of a
living thing, not merely of an irritated tissue fibril."
So they continued to study the thing. They examined
the discharges from other people showing symptoms of
the disease and they found the same peculiar thing in
each one. They at last decided that it was really a new
microbe and the cause of the disease. And later studies
of it proved conclusively that they were right.

While these dehcate Hving spirals were distinguished
under an ordinary immersion lens by the two keen-
eyed observers Schaudinn and Hoffmann, it was not
until they were examined on a dark field stage whose
brilliant side lighting illuminated very minute and deli-
cate forms that they could be seen with any degree
of clarity by the ordinary examiner. So their discov-
erers deserve all the more credit for finding them with
the help of only the ordinary immersion lens.

Another reason why they were not found before is
that they stain so faintly. Their discoverers tried many
staining methods, none of which made the spirals ap-
pear very distinct. The stain that brought them out
most clearly is a complex one known in its various forms
by the different names of its developers. The mixture
used by Schaudinn and Hoffmann for staining the
Treponema pallidum is known as Giemsa's stain. It
was a favorite stain for bringing out the structure of
protozoa. It is made up of a mixture of blue stains

THE COILED-HAIR FAMILY 207

(methylene blue and methylene azure) and of a pink
stain (eosin), and it brings out the structure of pro-
tozoa very well, but it only makes the syphiHs spirals
take on a faint azure stain. However, it differentiates
them from most of the harmless spiral forms that are
found in the mouth. These take a bluish color by the
Giemsa stain. Later, a method of silver impregnation of
these microbes was devised that shows the pale spiro-
chetes most spectacularly even in the tissues where they
appear by this stain as jet black spirals on a pale gray
background.

The announcement that a new microbe had been
found in that mysterious disease syphiHs, that at last
the probable cause of the disease had been discovered,
was received with great enthusiasm, and many research
workers started out to become better acquainted with it.

First they tried to see if it would grow outside of
the human body in pure cultures, just as most bacteria
do. But though they gave it every kind of food they
thought it might hke, it wouldn't grow for them. It
gave no sign of multiplying.

Just before the discovery of this spirochete, Novy
and MacNeal in Ann Arbor had succeeded in getting
pure cultures of a blood parasite belonging to the
protozoa, a flagellate relative of the microbe that
causes Oriental sleeping sickness. This was the first
and, until some time later, the only protozoan that was
cultivated in pure cultures.

Partly because of the apparent inabihty to grow the
syphilis spirochete and partly because its discoverers
thought it resembled certain protozoa, it was classed
by them with these lowest animal forms.

But when the bacteriologists began to study it they

208 WHOS WHO AMONG THE MICROBES

insisted that it resembled the bacteria more than it did
the protozoa. The controversy waxed warm between
the two factions. The question as to the relationships of
this type of mi'^robe is not yet settled. Read Noguchi's
statement^ regarding it in his latest (and alas! liis
last) ^ contribution to our knowledge of the Spiro-
chetes.

This wizard among microbiologists, Noguchi, was
the one who finally succeeded in growing pure cultures
of the Treponema pallidum. He found that it cannot
grow when exposed to the air; in other words, it is
anaerobic. He found also that it needs a bit of animal
tissue in the fluid serum-water used for its growth. The
animal tissue, such as rabbits' kidney, not only sup-
plies it with food but it helps absorb any free oxygen
that may be present in the fluid. Theobald Smith had
called attention to this fact some years earlier when
he recommended the adding of a bit of fresh animal
tissue to a fluid culture medium to help secure anaerobic
conditions.

Noguchi studied many different varieties of spiro-
chetes, both in their natural habitats and in the pure
cultures he was able to obtain of them. His studies made
us better acquainted with the individuality of these
spiral organisms and of their relationships in the
family group.

In one particular his classification does not agree
with that of the Society of American Bacteriologists.
He accepts only five groups or genera in the family
and the S.A.B. accepts six.

^In "Newer Knowledge," p. 455.

' Noguchi died recently in Africa from yellow fever contracted
while studying this disease.

A corner of the New York City Health Department Wassermann
laboratory. The chief of the laboratory is "reading" a test
from the blood of a syphilitic patient

THE COILED-HAIR FAMILY 209

Certain varieties that Noguchi includes among the
Treponemas are considered by a number of observers
to be characteristic enough as a group to be given a
special name. The name Borrelia after Borrel was the
first one chosen for this group, so that is the name it
goes by now.

The first group in this family still retains the name
Spirocheta that Ehrenberg gave it so long ago. In
this group the largest spiral microbes are found. They
are not only distinguished from the other large forms
by their size, but bj'' having a distinct axial filament.
They may be found in almost every kind of water.

The next group or genus, called Saprospira, mean-
ing rotten or putrid coil, is found in sand containing
decaying animal forms (forominifera). It is composed
of large forms in which no axial filament is seen.

The third genus is also characterized by its size and
by its lack of axial filament. But it has a very striking
appearance. Around its body is wrapped a more or
less wavy membranous structure made up of numerous
elastic fibrils Hke a felt work of bacterial flagella. At a
glance it looks something like the undulating mem-
branes possessed by some of the flagellated protozoa.
This pecuhar spirochete lives as a harmless parasite in
the alimentary canal or crystalline styles of oysters
and other shell fish. It is called Cristaspira because of
the crest on its coil.

Among the remaining three genera are the spiral
microbes of greatest interest to man.

Among the species of the genus Borrelia, the most
important one, from man's standpoint, though it is
not the biologic chief, is Borrelia recurrentis. Here we
have another illustration of the changing of the older.

210 .WHO S WHO AMONG THE MICROBES

original name to one of a more recent date when some
new investigator establishes a new genus whose chief
is an entirely different variety.

This most important microbe among the Borrelia,
and the one first discovered and described, was orig-
inally given the name Spirillum obermeieri, after Ober-
meier, who found it as long ago as 1873 in the blood
of people suffering from relapsing fever. Then classi-
fiers decided that it belonged among the spirochetes.
So its name was changed to Spirocheta recurrentis.
When a new genus was created for the pallidum the
spirochete found in relapsing fever was put with this
genus, so the name was then changed to Treponema
recurrentis. When it was decided to make a new genus
of this group it was called Spironema recurrentis.
Then classifiers found that a similar form, discovered
earlier in a fatal blood poisoning disease of chickens,
had been described by two Frenchmen in 1903 and
called Borrelia gallinarum. Since this was the first time
a genus was described for this type of microbe, Borrelia
galHnarum became the biologic cliief of the genus, and
our spirochete of relapsing fever received the name
Borrelia recurrentis.

Can one wonder that people have difficulty in re-
membering which name has finally been* chosen as the
right one for some of our microbes.?

The disease caused by this organism is called re-
lapsing fever because the first attack of the six-day
fever is followed after an interval of about a week
by another attack, and sometimes by a third, a fourth
and even a fifth attack. The patient usually recovers.
In India, where many cases occur, from 5 to 10 per
cent, may die. There have been a great many cases in

THE COILED-HAm FAMILY 211

Great Britain and Ireland, few in America and many
in Africa and India. Before spirochetes were found in
these various cases, the disease was classed with typhus
fever. The fact that it occurs more frequently among
unclean persons who live in crowded dirty quarters
and that it may be conveyed by biting bugs makes a
relationship to typhus apparent.

Each strain of spirochete obtained from relapsing
fever in different parts of the world seems to have
serologic characteristics individual enough to give it a
separate specific name. So if j^ou want to meet all
the important Borrelias pathogenic in man you must
know that besides Borrelia recurrentis from England,
Ireland and other parts of Europe, there is a Borreha
duttoni found by Dutton and Todd in Africa, a Bor-
relia Novyi found by Shellack in American relapsing
fever, a Borrelia berbera, found by Sergent and Foley
in Algiers, Tunis and Tripoli and a Borrelia carteri,
found by Carter in India. All of these are ahke morpho-
logically but differ serologicall3^

The same kind of a spirochete with minor differences
has been found in a number of the lower animals as
the cause of a febrile disease. We have already men-
tioned the one causing fever in chickens. It is trans-
mitted by the bite of ticks. Another variety causes a
relapsing fever in cattle, another in geese.

Then there have been varieties found in the blood
of mice, in the stomachs of flies, and in the blood and
ulcers of hogs suffering from hog cholera. These are
no doubt secondary invaders. There are also forms
found on the mucous membranes of man in association
vdih bacteria. Most of these are probably harmless
parasites.

212 WHO S WHO AMONG THE MICROBES

Now we come to the point of considering more in-
timately that worst member of the spirochete family,
the Treponema pallidum.

What volumes have been written of the activities of
this microbe! How that disgusting disease it causes,
the great pox, the running issue, the scab, the botch,
lues, syphilis, venereal disease, to mention some of its
names, is spoken of with lowered voice in the presence
of the innocent. How it shocks moralists to learn of
each new victim.

For this is the immoral disease. Indeed, during the
fifteenth and sixteenth centuries, when immoraHty was
so rife, when chastity was considered harmful and
license was encouraged, when wars and crusades helped
its spread, it became a veritable mahgnant pandemic.
All were said to be infected with the "bad disease,"
with venereal diseases, for gonorrhea or gleet was in-
cluded with syphilis. And no one then knew about the
nature or cure or prevention of these diseases.

It was during this time that the name syphilis came
into use.

That famous Veronica physician, Fracastorius, who
was one of the first to speak of diseases being conta-
gious, wrote, in 1530, a "poem" about a swineherd
whom he called Sypliilis, from two Greek words which
mean, I love a sow. In this he declared that this swane-
herd Syphilis was the first person to have this dreadful
pox, and that it was inflicted upon him by God in
punishment for his blasphemies against God as the sup-
p-^sed author of a deadly blight among the herds
SyphiHs was tending.

The real origin of the disease is lost in antiquity.

As knowledge grew of how the disease was trans-

THE COILED-HAIR FAMILY 213

mitted and how it might be prevented, its ravages
among the more enhghtened became somewhat re-
stricted, but even now, when we know definitely how to
prevent it, it is still one of the most \Nade-spread of
human ills. In those parts of the world like the United
States, where it is less frequent, it is estimated that at
least one tenth of the population is infected with Tre-
ponema pallidum, and in those parts of the world where
pubhc health has not been developed into an efficient
social activity the number of inhabitants estimated
infected is put as high as 60 per cent.

This lack of control of the pale spirochete is due
chiefly to the fact that the measures recommended for
stopping its inroads are so closely associated with ques-
tions of sex, morality and alcohohsm, all fundamental
social questions. People often stimulated by alcohol
give way carelessly to their passions, regardless of the
results. Then when they come to their senses and realize
that they may be infected they are ashamed to have
it known.

This means that the doctor doesn't see the case
until too late to effect a quick cure, and so too late
to stop its spread, often to innocent victims. When one
realizes that the innocent ones may be among the un-
born children, who fortunately for them may be born
dead, or unfortunately for them may show terrible
signs of the disease after birth, or, most unfortunately,
may show no sign of this insidious disease up to twelve
years of age or even older — when we think of this we
say, Away with shame! Either do away with prosti-
tutes— male and female — ^those vicious hnks in the cycle
of deterioration of human beings, or, until that time
comes, for it surely will come, urge cases to report

214 WHO S WHO AMONG THE MICROBES

promptly and be treated immediately. Whether the in-
fected one be victim or culprit should have nothing to
do with interfering with his having the benefit of the
marvelous results from the present-day treatment.

Even if the one infected does not consult a physician
immediately, while he runs the risk of infecting others,
the damage to himself may not be great until much
later. All through the primary and secondary manifes-
tations of the slow progress of the Treponema palhdum
through man's tissues its victim may be cured (with
always the occasional exception) by one or both of two
drugs. First there is mercury, one of the oldest drugs,
the effects of which in syphihs have not their parallel
in medicine. Then there is that wonder among drugs,
arsphenamine, or the 606th preparation from arsenic
that Ehrlich developed after researches that are re-
counted so thrillingly by De Krief in his "Microbe
Hunters." Bismuth is also much used.

Of course, these powerful drugs must be given under
the close supervision of experts, and their use some-
times extends over long periods of time. They attack
and kill the deadly Treponema directly, and usually,
when properly given, do no harm to its host.

The favorable results from treatment are determined
by that complex test the so-called Wassermann re-
action that we mentioned in Chapter IV. This test
indicates whether or not the Treponema pallidum is
alive and actively carrying on its work of destruction
in the tissues. So the test is used in the first place
in helping to detect infection, and in the second place
to determine when the drugs used have killed the
microbe.

Other tests have been used for this same purpose,

THE COILED-HAIR FAMILY 215

such as Kahn's and Kline's precipitin tests, which are
not as cumbersome as the original Wassermann test,
and seem to be just as true indicators. But before any
such test is substituted for an established one, a large
series of control observations must be made. This is
just what we are doing now in different laboratories.

There are two chronic nervous affections of man
that used to be called parasyphilis, one jumping palsy
and the other a kind of insanity. When Noguclii in
1913 demonstrated in the brain and spinal cord of
these cases the presence of the Treponema pallidum, it
was recognized that these conditions should be added to
the already protean conditions caused by tliis sinuous
and insidious microbe. They are late syphilis of the ner-
vous system.

At this late stage of the disease, when there may be
evidences of the destruction of tissues throughout the
whole body, it may be too late to get any good effects
from drugs. Potassium iodide is given at this stage to
help resolve the inflammatory conditions of tissue cells.

The near relations of the Treponema pallidum —
that is, the other members of this genus — are few, and
most of them are probably only harmless parasites on
the mucous membrane of man's orifices. Noguchi was
the one who first grew these in pure cultures and studied
them minutely enough to name them, with reasonable
assurance that the names would hold, at least until
other workers could become better acquainted with
them.

One of those not included as harmless parasites is so
like the pallidum in appearance that it cannot be dif-
ferentiated morphologically. It was found by Castellani
in a disease very similar to syphilis occurring in the

216 WHO S WHO AMONG THE MICROBES

tropics and known by the name of yaws, peon or fram-
besia. Castellani maintains that it causes the production
of specific antibodies in experimental animals, and that
therefore it should be considered a different species. It
is called Treponema pertenue.

A Treponema very like the palhdum has been found
in a spontaneous venereal-hke disease of rabbits. Tliis
is a very important discovery from the standpoint of
the research worker, since rabbits are used so often in
studies of the palhdum. However, Noguchi has pointed
out differences between them which seem to differentiate
them. He gave it the name Treponema cuniculi.

A Treponema was found in pond water by Wolbach
and Binger that was sho\Mi by them to be filterable.
Novy and Knapp had shown a half dozen years before
that the Borrelia may pass through a stone filter. The
question of the filterability of this type of microbes is
of special interest since the finding by Noguchi of a
spirochete in one of the dreaded diseases of the tropics,
3'^ellow fever. For a time it was considered to be the
cause, but now it is thought to be only a secondary
invader, and the real cause of this disease is again
attributed to a filterable virus.

It is interesting to recall that two of the biggest
scourges of mankind are among the diseases attributed
to this tj^pe of microbe, and that both were brought
practically under control before the organisms said
to cause them were discovered — one, syphilis, by the
power of mercury ; the other yellow fever, through the
wonderful work of the American commission which will
be described in the chapter on filterable viruses.

The spirochete found by Noguchi in yellow fever

THE COILED-HAIK FAMILY 217

is the most minute among these forms. It has tightly
set regular shallow spirals, very similar to the forms
found a short time before by two Japanese investiga-
tors, Inado and Ido, respectively in the two disease
infections jaundice and seven-daj's fever. Noguclii con-
sidered that a new genus should be created for the three
forms, for wliich he proposed the name Leptospira,
which means fine coil. He called this new spiral microbe,
which he thought was the cause of j'ellow fever, Lep-
tospira icteroides. Then he found that Stimson, way
back in 1907, had found a spirochete in the blood of
yellow fever patients and named it Spirocheta interro-
gans. Xoguclii, after examining Stimson's prepara-
tions, came to the conclusion that the spirochete he saw
in them was probably the same as the one he had just
found. These tissue spirochetes have a way of hiding
themselves that makes them hard to find. This is the
reason, said Noguchi, that no one had found them in
yellow fever in the meantime.

So the name of this spirochete also is changed. It is
now known as Leptospira interrogans. The name in-
terrogans is descriptive of the characteristic hooked
ends, Hke interrogation marks.

Noguchi studied liis spirochete in many ways, but
notwithstanding all the evidence he brought forward in
favor of his spirochete being the culprit in yellow fever,
the majority of other observers who have followed his
work with interest and appreciation consider that it is
probably only an adventitious invader.

Indeed, Noguchi himself was in doubt as to its being
the cause of the disease called yellow fever in other
parts of the world. And the results from the recent

218 WHO S WHO AMONG THE MICROBES

investigations of African yellow fever, including the
tragic death of Noguchi there from the disease while
studying it, have all given evidence that yellow fever,
at least in some parts of the world, must still be listed
with filterable viruses.

CHAPTER XVI
THE BRANCHING FAMILY

(Actonomycetaceae)

The lumpy-jaw microbe — Infrequent but insidious attackers
of human beings — Decomposers of organic matter.

As a probable link between the bacteria and the molds
the branching family occupies an important place in
the considerations of the systemic classifiers. The ten-
dency of its members to form branches as do the molds
is a significant characteristic that favors the idea of
close relationship to this higher class of plants. On the
other hand, the fact that their slender branched fila-
ments break up freely into unbranched bacilli and
coccal forms looking exactl}" hke the bacteria is in
favor of their closer relationship to these lower plants.
When those that invade man are first found groT\ang in
the body fluids they usually present this appearance of
small bacilli or cocci, hence if not isolated and studied
in pure cultures they may be mistaken for lower bac-
teria. But in their mass appearance in cultures many
of them resemble strongly the molds. They make a
tough dry wrinkled growth on the surface of the food
medium that sends tenacious strands down into the
depths of the medium where they may become firmly
attached.

Sometimes their surfaces are covered with the down
of aerial branches. Some of them form end spores more

219

220 WHO S WHO AMONG THE MICROBES

like certain molds than bacteria. In fluid media they
form fluffy white balls that look very much hke most
molds. It certainly looks from tliis description as if
Castellani and others were right when they placed those
forms with the molds.

Not only is their family position in dispute, but the
relationships of the cultures obtained from different
sources are still largely unsettled. This puts us in more
doubt than with most groups as to what we should call
them.

We know we shouldn't call them streptothrices, be-
cause that name has been preempted. But shall they all
be called Nocardia after the Frenchman Nocard, who
first described an important microbe of this type in a
farcy-like disease of cattle? Or shall they all be called
actinomyces or ray fungus, the name first given to
another culture of this type obtained by Harz in 1877
from a similar disease in cattle ? Or shall they be divided
into two groups or genera as some think they should,
those producing definite spores called Nocardia and
the other, in which definite spores have not been seen,
called actinomyces.'^ Or shall the name actinomyces be
dropped entirely even as family name, as does Castel--
lani? Or shall there be still other genera to mark more
minute differences, as others have recommended?

These are some of the serious questions that are
occupying the attention of our classifiers who are study-
ing this group.^

Whatever our uncertainty at this stage of our ac-
quaintance with them about accepting generic and

^See Castellani, "Fungi and Fungus Diseases." Am. Med, Assoc.
Chicago, 1928. Also Buchanan, "General Systemic Bacteriology." Bal-
timore: Williams & Wilkins Company, 1925.

THE BRAXCHING FAMILY 221

Specific names for cultures from different sources, of
this we are sure :

Microbes having in common the characteristics as-
cribed to those we have called the liigher bacteria, or
branching bacteria, are found frequently in the soil,
less often in plants and comparatively seldom in man
and lower animals.

In the soil many of them produce enzymes that play
an important helping part in breaking up organic
matter into ammonia, carbon dioxide and water. They
assist the molds and the bacteria in this decomposition,
or the changing of these materials into forms to be
absorbed by the higher plant roots. IVIany varieties of
this type have been described by Waksman ^ and others
as existing in the soil.

In higher plants, while some forms appear to be
harmless parasites, a few varieties are known to cause
destructive diseases. Thus, the different scabs on plants
are due to varieties of actinomyces. These may be car-
ried, probably only mechanically, by the aphis, that
httle plant louse, green, woolly, or other kinds that
may grow to enormous numbers and soon cover the
leaves of our delicate plant shoots and suck their juices.

In lower animals, particularly in cattle but occa-
sionally in horses, sheep, pigs, goats and elephants, this
type of microbe may cause serious diseases that may
resemble tuberculosis or glanders (farcy). Animals pas-
turing in river valleys and other moist lowlands are
more Hable to contract it than those on the higher hills.

The organism which commonly attacks first the
lower jaw or the tongue or the neck tissues is sup-

* Waksman, "Studies in the Proteolytic Enzymes of Soil Fungi and
Actinomycetes." "Jour, of Bact.," November 3, 1918.

222 WHO S WHO AMONG THE MICROBES

posed to gain entrance through a wound, however
small, that may be made by a bearded grain or any
coarse rough forage containing the spores. The disease
is often called lumpy jaw because of the sweUing often
formed on the lower jaw. The meaning of the term
lump is incorporated in the name actinomyces. It is also
called wooden tongue because of the swelling and
hardening of the tissues of the tongue through infil-
tration with inflammatory cells. There may be swellings
also on the neck forming a sort of wen. All of these
swellings may gradually break down in the center,
forming a collection of pus or an abscess.

Stained sections of these disgusting-looking abscesses
examined under the microscope may appear very beau-
tiful— at least to the pathologist. The small yellowish
or greenish-yellow granules of pinhead size seen by
the naked eye scattered through the pus or in the
tumor-hke granulation tissue, through the lens are seen
to be made up of striking-looking rosettes. These are
the microbes that cause the disease. Their growing in
these characteristic ray-like rosettes, combined with
their causing so often a lump in their host's tissue, is
the reason that Herz gave them the name actinomyces,
and the reason why the disease they cause is called
actinomycosis.

In the center of these older rosettes is a bunch of
short threads, rods and granules. Radiating out from
this center are many Indian-club or pear-shaped forms
which are ends of the microbes that enlarge as they
come in contact with the tissues. With the double pink
and violet Gram stain the bacillar and coccal forms re-
tain for the most part the violet stain, being Gram-

THE BRANCHING FAMILY 223

positive or nearly so (Grara-amphophile). The Indian-
clubbed ends lose the \aolet stain by Gram's method of
staining and take the pink stain so intensely that they
appear glistening.

In man, alas! some of these branching forms also
cause dangerous diseases; and they are among the in-
sidious attackers. We don't know when they enter, and
hj the time they make their presence felt we can seldom
trace their mode of entrance.

While they infect few people, they are more incrim-
inated than earher, particularly throughout the upper
Mississippi Vallej" and parts of the Northwest States.
At the ^laj'o clinic in Rochester, Minnesota, Sanford
reported 157 cases in nine years (1913-22). At the
Massachusetts General Hospital, sixty-three cases came
under observation during the twenty years before 1922.
Seven hundred cases were reported in the whole United
States up to 1923.

If the person affected doesn't put up any resistance,
the microbe may pass slowh^ through the blood vessels
and become deposited in different tissues, causing a col-
lection of tissue cells at that point which finally break
down into abscesses, in wliich may be found the charac-
teristic httle dirty-looking yellow particles that are
made up of the same kind of rayed rosettes found in the
abscesses of lower animals.

If these abscesses are formed in the lungs the diag-
nosis may be easily made by finding the httle yellow
grains of rosettes in the sputum. Crushed under a cover
glass and on a glass slide and then examined under the
microscope, the rosettes can be seen even without stain-
ing, but staining makes them more easy to find. Some

224i who's who among THE MICROBES

varieties of these microbes do not make rosettes in tis-
sues, and none of them form these striking growths
readily in cultures.

Whether the microbe may be normally present in
the mouth for any time ready and able to invade the
blood stream and tissues whenever a wound is made and
the person's resistance allows it, or whether it is only
taken in with the food from time to time, is a moot
question, as is also the question of the part played by
at least some of these microbes as secondary invaders.

That they may be in carious teeth has been clearly
demonstrated by the fact that the injection of the
contents of such a tooth into the peritoneal cavity of a
guinea-pig has been followed by the development of
actinomycosis in the animal. But just w^hat part they
have, if any, in bringing about the caries of the tooth
is not clear.

Castellani has described a number of cases of chronic
tonsillitis, occurring commonly in the tropics, that he
considers are due to this type of microbe. He says that
the tonsillar crypts become plugged with a yellowish-
white mass consisting of a number of different kinds of
microbes, chief among them being these slender branch-
ing forms. The whole mass may emit an offensive odor,
which is usually the cause of the patient consulting the
doctor. That the germs collected in these crypts are
not of the usual invading type is shown by the fact
that they simply stay in the crypts, accompanied by
only slight enlargement of the tonsils, and that they
are easily removed and the condition cleared up by
proper treatment.

What such forms might do in the occasional non-
resistant case we don't know. We do know, however,

THE BRANCHING FAMILY 225

that a few abscesses of the brain have been found to
be due to this type of microbe, also a few cases in which
the Hnings of the brain are the parts they attack.

Only eighteen cases of this kind of meningitis have
been reported in the whole world, according to Dr.
Neal. But all of these cases died. The majority of these
cases had been suffering from middle ear infection, so
presumably the branching organisms were in the pus
of the ear and reached the meninges from this source,
but no definite evidence was given that this was the case.
In these brain cases the course of the apparent disease
may be very short.

One of the cases seen by Dr. Neal, the one in con-
sultation with Dr. Elmendorf, may be cited as an illus-
tration of how such infections may finally give evidence
of their presence in the brain and what a rapid course
they may run. No point of entry could be determined.
The boy, a child of twelve years, had seemed well for
some time before. It is true he had been a "blue" baby
and he had always been a delicate child, but he had
been well cared for and during the past half dozen
years had seemed reasonably healthy and had had a
comfortable Hfe.

One day after he had returned from a trip to Vir-
ginia he complained of a headache which lasted only
a short time. During the next few days he complained
again several times for a little wliile at a time of
having a pain in his head. His parents thought he was
merely a little upset by his trip, but he continued to
complain off and on of a head pain. So his parents
called in the family physician. He couldn't find any
cause for the headache. During the next few days the
child developed a low irregular fever and he vomited

226 iWHO S WHO AMONG THE MICROBES

once. Then suddenly eleven days after he first com-
plained of his head he became much worse. He went
into convulsion after convulsion. At this time the chief
of the division caring for the meningitis diseases of
the Health Department, Dr. Neal, was called in con-
sultation.

Of course, by this time there was no question but
that the child had meningitis. So the laboratory doctor
took fluid from the spinal canal and gave the child
serum. The spinal fluid was taken to the laboratory
and submitted to the usual rigid examination. Then
they put some of it under the microscope to look for
the microbe that usually causes meningitis, the menin-
gococcus. But they didn't find the characteristic Gram-
negative diplococci. Instead they found innumerable
minute Gram-positive and Gram-negative cocci, with
occasional bacillar forms. What was it? "That," said
the chief examiner, to whom the specimen was referred,
"looks very like one of those higher bacteria that will
show branches if you put it in a right environment.
Wait until you see what you get from the cultures
you have made."

When they examined the cultures after letting them
grow overnight at blood heat in the incubator they
found no growth on the surface of the culture medium
that always shows a growth of the meningococcus, when
present. Then they looked at the tubes of the broth
and serum medium in which they always place a little
of the material to be examined and pour over the top
some hquid vaseline in order to give those microbes
that cannot grow on surface in the presence of air a
chance to grow. And there they found a delicate cloud
at the bottom of the tube of this medium.

THE BKANCHING FAMILY 227

Examining a drop under the microscope, they found
that the cloud was caused by a groAvth of a dehcate
thread-hke microbe ^'ith an occasional branch and
many coccus forms. On further study, giving it the
sugars this kind of microbe particular!}' hkes, it in-
deed proved to be a branching microbe — an acti-
nomyces. The child died in three days from the time
it began to have conATilsions.

The microbe obtained from this case was, as we said,
an anaerobic variety of the branching germs. From
other cases, especially from lung infections, cultures
have been obtained of a microbe very similar to these
anaerobic forms, except that they will grow in the air —
that is, they are aerobic. These aerobic cultures are
more apt to form the spore-like bodies that some people
think should be a basis for grouping them under a
separate name.

Varieties of these branching microbes have been
found in skin diseases. In one of these conditions a
purulent inflammation of the foot, called mycetoma or
Madura foot, occurring in warm countries, a variety
of actinomyces, is accepted as the cause of the disease
as it occurs in India (Vincent), and another variety
in a similar condition occurring in the Philippines
(Musgrave and Clegg).

In certain cases of rat bite fever, Blake, INIinsnerkoff
and others have found actinomj'ces-hke organisms in
the blood. In some cases of pj^elitis, or inflammation
of the bladder, an organism of this type has been pres-
ent, but just how much harm it is capable of doing is
not determined.

In a certain febrile disease of cattle a thread-hke
bacillus called actinobacillus has been found. It is con-

228 WHO S WHO AMONG THE MICROBES

sidered a near relative of the actinomycetes. In an ery-
sipelas-like disease in swine an actinomyces-like microbe
has been found called erysipelothrix. It is considered
the cause of the disease.

In all cases where an actinomyces infection is sus-
pected potassium iodide should be given in large doses,
since in some cases it has had a remarkably quick cura-
tive action, in both man and beast.

If given to milch cows, it causes the milk to dry up.
In market animals, when the condition is local, the
diseased parts may be cut out and the rest of the
meat put on the market.

CHAPTER X\^I

YEASTS AND MOLDS

Alcohol producers — Bread raisers — Cheese flavorers and

ripeners — Decomposers of organic matter —

Infrequent producers of disease.

It is little wonder that much was learned about molds
and yeasts long before knowledge of bacteria became
general. They are so much bigger than bacteria and
grow in such conspicuous ways, from mushrooms to
ergot, that they thrust themselves upon one's notice.
An ordinary hand lens magnifies enough to show, in
some varieties, the beautiful fruiting branches wa\'ing
in the air, and a httle higher magnification reveals the
interlacing filaments or threads (myceleum) of the
molds and the budding cells of the yeasts.

Moreover, they are found everywhere. Their minute
fruits, often containing many seeds or spores, have so
Httle weight that they may be carried far by even a
breath of air. They are so resistant to unfavorable sur-
roundings, such as heat, cold, lack of moisture, and
so on, that they are not easily destroyed and they may
remain quiescent for an indefinite time. Then, with any
encouragement, the spores sprout and begin to grow
rapidly.

Such varieties need only the slightest amount of
moisture to enable them to start growing, and they
find food in the most unlikely places. Once finding it,

229

230 WHO S WHO AMONG THE MICROBES

if they be undisturbed long enough they grow luxuri-
antly.

Thus they grow on old leather shoes, covering them
with irregular green patches that might be considered
beautiful elsewhere. They invade our rugs, stuffed fur-
niture and bedding, developing an unpleasant musty
smell during damp summer months if these household
furnishings are not frequently and thoroughly beaten
and exposed to sunny air.

They are very fond of sugar, so if given half a
chance, they cover our jellies and jams. Some varieties
grow even in raw sugar, where they may cause con-
siderable damages in commerce.

They may grow upon and in all kinds of exposed
food, thus spoihng it at least for our taste. So, while
the vast majority of them give no evidence of attacking
man's body, they manage to make themselves very
disagreeable or at least apparently useless: except —
and there is a big except — some varieties were early
found to produce effects that are both agreeable and
useful to man, and a few varieties, alas! have shown
themselves able to attack him and cause serious disease.
In fact, a mold was the very first microbe that was
accused of causing a disease. In the little yellow cups
of favus, a disease of the scalp, a microbe was found
by the German Schonlein as early as 1839, and was
thought by him to be the cause of this skin disease,
though other observers at that time thought that this
was a peculiar hypothesis.

In the next few decades molds were found in several
other obvious skin diseases, but interest in them as
human disease agents died down when the more spec-
tacular facts in regard to bacteria and disease were

YEASTS AND MOLDS 231

brought to light. In later years other varieties of this
type of microbe have been convicted of causing dan-
gerous diseases in man, beast and plants.

In the meantime, the interest in those forms that
were found to make man's hfe seem more enjoyable
and useful to him continued to increase, until now
we have great industries whose products are aided by
the employment of these agencies.

So there is no question about the important role
played by the yeasts and molds in the hfe of man, in
both helping and hindering his — shall we call it.'' —
progress.

In the first place, let us consider those useful vari-
eties that have helped form great industries. Chief
among them are certain yeasts. Doubt, nay, absolute
conviction, is found in the minds of many as to the
value to man of the principal use to which these yeasts
have been put. For they are the great agents in pro-
ducing alcohol.

What a drama in the world's history of microbes
was the discovery that yeasts make alcohol out of sugar ;
that Hving things cause fermentation ; that yeasts fer-
ment grapes and other fruit into wine which may be
changed into brandy ; that yeasts make beer from bar-
ley, com wliisky (moonshine whisky) from corn ; whisky
"the breath of hfe," from man}^ different grains ; that
they make alcohol from beets, from molasses, from any
material containing sugar, and allowing them to grow.

What years of brilhant experiments and telhng dem-
onstrations were made by Pasteur and others in their
efforts to show the world that the early discoverers, La-
tour, Kutzing and Schwann, were right, and that Liebig
and others were wrong; to show that fermentation

232 WHO S WHO AMONG THE MICROBES

really was caused by these little budding microbes and
that alcohol was produced through their agency.

Since that time much has been learned in regard
to the best yeasts to use and the best methods of grow-
ing them in order to produce certain results in the
making of alcohol in general, and in the manufactur-
ing of wine, beer, brandy and other alcoholic beverages
and medicines, in particular. Metaphoric and rhetoric
use might be made by the "drys" of the fact that the
alcohol produced by the yeast finally kills it. At any
rate, real use is made of this fact by the manufacturers
of spirituous liquors in their clearing of the products.

What clever experiments were made also by Pasteur
to show how "wild yeasts" and certain other microbes
interfere with the making of good alcohohc liquors.
Much research has been carried on as well concerning
the mechanism of the reactions in the production of
alcohol.

Certain yeasts also play a part in another famous
industry. This is due to a further power they have,
that of forming a gas in their growth. This role, of
course, is played in the making of bread. Every one
knows yeast cakes and the great industry that has
arisen from their power to "raise bread," to make it
porous and light. And not only do cooks add them to
their ingredients for making bread, but many people
have eaten yeast cakes directly, with the hope of cur-
ing certain gastro-intestinal and skin disorders, such
as constipation and acne, or of adding more vitamins
to their diet. The hope for yeast being of use in these
diseased conditions has not been realized. The yeast
seems to have no inhibiting effect on the putrefactive
bacteria in the intestinal canal, and, while constipation

YEASTS AND MOLDS £33

is relieved in some cases, in others diarrhea develops,
so some observers think that yeast eaten in quantity,
while usually harmless, might sometimes be harmful.

One of the by-products in the manufacture of alco-
hol from yeast is glycerin. By the usual method only
a little is produced ; but during the World War, when
glycerin was wanted and the supply was low, several
people made attempts to get an increase from this
source. Finally, two Germans found that if fermenta-
tion was carried on in an alkaline solution much more
glycerin was produced.

Other studies of yeasts being carried on at present
may jdeld still more interesting results.

A variety of the yeast group is an active agent in
the ripening of Swiss, Belgian and other cheeses. In
the making of some cheeses certain molds are used.

In Roquefort cheese the green color is due to the
common mold Penicilhum glaucum. This is considered
such an improvement to the flavor of the cheese that
it is the practice to sow it purposely in the cheese mass.
This is done by allowing bread to become covered with
a rich groT^i;!! of mold, then drying and grinding it
and spreading the resulting powder between the sepa-
rate laj'ers of the shced curd. In several other cheeses
also molds have been used to improve their quahty.

The molds have been used by humans in a number
of other ways. Thus, certain molds have an active
power in breaking down or fermenting various sub-
stances besides carbohydrates by their special enzymes,
so that these substances are in form to be fermented
by yeast cells. In Japan, in the production of spirit-
uous hquors like that Japanese alcohohc drink known
as sake, rice is acted upon first by a mold of the

234 WHO S WHO AMONG THE MICROBES

Aspergillus group, and then by a yeast. Another va-
riety is used for making a special preparation from
the bean. A number of these mold enzymes have been
patented in Japan and placed on the market.

Several organic acids are manufactured through the
agency of mold fermentations, notably gallic acid from
tannin and citric acid from granulated sugar. Thom ^
in' his interesting sketch of one of the most representa-
tive of the molds, the Aspergillus, describes more fully
the points given above and many others.

He calls attention to an interesting habit of the
fruits of some of these molds. When growing on a
medium that is neutral they are purpHsh in color. If
an alkali is added to the medium, they turn blue; if
an acid is added, they turn red. Thej'^ might thus be
used as an indicator in determining whether an or-
ganism produces acid or alkah in its gro^^i:h.

Waksman ^ sums up our knowledge of the important
part played by molds in the decomposition of organic
matter in the soil. Different molds attack different
substances. Thus mucor molds attack the proteins and
the hemicelluloses, but not the true celluloses, or the
tannins or certain others, while Aspergillus, Penicilhum
and several other varieties break these up into simpler
constituents. The decomposition of these substances is
helped largely by certain bacteria, as we mentioned
in Chapter VII.

Now^ we come to the varieties of the molds and the
yeasts that exert a harmful action on man. The ma-
jority of those that attack man invade the skin and

* Thom. "The Aspergilli," in "The Ne%ver Knowledge of Bac-
teriologjs" etc., p. 437. "University of Chicago Press, 1928.

* Waksman, ibid., p. 315.

YEASTS AND MOLDS 235

hairs only. But a few penetrate deeper, and these may
be so insidious and persistent in their growth through
the tissues that, if not discovered and treated in time,
they may finally kill their victim. The more super-
ficial growers may only cause baldness, the loss of
finger nails, disagreeable itching, spotting and pim-
pling of the skin, and so on.

Not only are there those that harm man thus di-
rectly, but there are many varieties that cause in-
direct harm to man in instigating wide-spread plant
epidemics. Potatoes, oats, wheat, cotton, many fruits
— all may be attacked. Whole coffee plantations have
comparatively suddenly disappeared in Ceylon, says
Castellani, through epidemics caused by fungus.

Varieties of microbes all among the molds that cause
certain skin disease in man were the first to be dis-
covered in those attacking the hairs and the earliest
to attract attention. These occur with greatest fre-
quency in the tropics and usually among people who
are careless in habits of hygiene. But northern coun-
tries are by no means free from them.

Favus, in which little yellow cups are formed about
hairs ; the various kinds of ringworm, that danger from
unclean barber shops; the mange, that may make our
dogs and other animals unsightlj^ ; tinea flava, causing
a loss of pigment in the skin, making Hght spots on the
dark skin of southern natives, which are considered
beauty spots by them — all of these and a number of
other skin diseases are due to molds. Most of these were
seen for the first time about the middle of the last
century. While they were accused by their discoverers
of being the cause of the conditions in which they were
found, by many observers they were not believed to

236 WHOS WHO AMONG THE MICROBES

be the cause. As time went on, with the help of many
investigators and of experiments on volunteers it was
finally proved that certain molds caused these diseases.

Then it was found that yeasts could cause pustules
and ulcers in the skin, that these may slowly increase
in numbers, and that the yeast may finally travel
through the whole body, producing abscesses wherever
they may lodge and finally causing death.

The first papules and pustules formed by the yeast
are not painful, so in the beginning they may not be
taken care of properly, and then by the time they
are recognized as harmful it may be too late for any
good effect from the potassium iodide which we usually
give in these cases.

The question of the relationships of the various
strains of yeasts isolated from human disease is still
far from being settled, but this does not interfere with
the practical point of diagnosis, nor with the knowing
how to treat those who are infected.

One of the first invaders of human beings among the
yeasts was discovered by Busse in 1894. The yeast
appeared first in an abscess of the tibia, then gradually
it infected lymph glands, lungs, kidney and spleen. It
took over a year to kill its victim. In the majority of
the generalized infections ending fatally the lung has
been the chief site of gro\^i;h of this kind of microbe.

It often looks something Uke a protozoan growing
in the tissues, and was first said to be one of the animal
microbes. Then Orphuls showed that it could grow and
put out myceHal threads like a yeast mold.

The brain of humans too is not exempt from in-
vasion by this type of microbe. About the same num-
ber of people have been reported as having a fatal

YEASTS AND MOLDS 237

brain infection of yeasts as those killed through brain
infection b}' actinomyces. The course of the disease is
generally longer than in actinomyces infections. Here
is a sketch of a case Dr. Neal saw in consultation with
Dr. Shapiro:

In New York, a boy sixteen years old had always
been reasonably well until February, 1923, when he
complained of left frontal headache, of weakness and
of sleepiness, wliich persisted for about one week. At
this time he did not appear to be suffering from any
acute or chronic disease. His mentahty was normal,
and physical examination especially of the nervous
system, eyes, ears, nose and tissues was negative.

Suspecting encephahtis, he was kept at home an-
other week ; at the end of that time he felt so well that
he returned to his private school.

He was well until May 15, when, after eating a
large quantity of chocolate cake and pie, he suddenly
developed a similar left frontal headache with vomit-
ing, weakness and dizziness, which continued off and
on. Not responding to systematic treatment, he was
sent to a sanatorium on May 23. Physical examination
at this time was negative, except for a loss of fifteen
pounds (6.8 kg.) in weight since February. Mentally,
he was normal until the evening of IVIay 25, when
he suddenly became dehrious. This lasted but a few
hours. Five daj^s later the patient complained for the
first time of pain in the back of the head and neck,
sUght disturbance of vision and photophobia. From
then on e\ddence rapidly developed that we were deal-
ing Tv^th an acute infection of the central nervous
system, particularly of the meninges.

Lumbar puncture was performed for the first time

238 WHOS WHO AMONG THE MICROBES

on May 29. The fluid was found to be under very high
tension and sHghtly hazy in appearance. There was
no growth in the culture of the fluid the first eighteen
hours, but distinct yeast colonies were apparent on the
following morning, May 31, thereby estabhshing the
diagnosis of a yeast infection of the central nervous
system. Lumbar punctures, which seemed to offer him
some relief, were subsequently made daily until near
the end, and the torula organism was recovered from
the fluid by culture and observed in smears. He became
gradually worse and died about eight months after
first being seen.

The iodine treatment as well as various other reme-
dies tried seemed to have no effect.

These microbes certainly have a way of keeping right
on growing in the exceptional case once they get
started.

One of the definite molds called Sporothrix has been
found in quite a number of skin diseases and in a
smaller number of general infections in man.

In this infection if given in time potassium iodide
may be said to be a specific cure.

CHAPTER XVIII
ANIMAL MICROBES OR PROTOZOA

The amoeba as a fighter — The misnomer malaria — Protozoa in
mosquitos and man, in ticks and Texas fever — Sleep-
ing sickness and the boring animal — The
animal causing dum-dum disease.

Microscopic animals are neither as wide-spread nor as
numerous as are microscopic plants ; moreover, those
animal germs that are definitely harmful to man are
all parasites. There are no free living — saprozoic —
varieties kno^Mi among them. None of the varieties that
cause disease in man have been shown to be able to
multiply outside of an animal under natural conditions.
Of course, those that form cysts may exist for a variable
time in a quiescent state outside of their animal hosts.
The majority of those that attack man are met with
commonly in tropical countries.

Neither are the protozoa easily transmitted from man
to man. Indeed, most of them are transmitted chiefly
if not only through a second host, commonly a biting
insect, in which they must usually undergo a period
of development before they can infect man. So these
forms do not cause definite epidemics. Rather they
are endemic in certain localities.

While many of these animal microbes are not directly
harmful to man, not many, if any, are known to be
helpful to him. It is true that some of the protozoa in

239

240 WHO S WHO AMONG THE MICROBES

the soil which may be teeming with flagellates and
amoebas may help decompose organic matter and pre-
pare it for plant growth. But on the other hand, some
observers claim that the soil protozoa eat up the bac-
teria that are the most helpful aids in the hfe cycle
of plants and animals. Thus they really make the soil
less fertile. As evidence in favor of this idea the fact
is cited that partial sterilization of soils that kills off
most protozoa results in greater fertihty for the higher
plants.

The first protozoan introduced as a disease pro-
ducer in man was an amoeba, that microbe favored as
the type of our beginning. But what its relationship
was and is to others of the amoeba family we cannot
say. For, alas ! here again the descriptions of the form
first seen, in dysentery, by Losch, away back in 1875,
and the varied attributes claimed for varieties intro-
duced since then, leave one in doubt as to whether or
not this first one is an ancestor or other relative of
any of the later ones.

How hmited is our field of vision and how quick
we are to draw deductions from a few one-sided ob-
servations ! All research tells the same story. Again we
must say that it is only the exceptional one that sees
clearly, that checks or controls his observations at every
step and that is slow to draw deductions. The story of
the introduction of the pathogenic and the saprogenic
amoebas is a striking illustration of the truth of these
laments.

We are still not sure how many varieties of amoebas
cause disease, but we know, from the fine work of Coun-
cilman and Lefleur and others, that one at least, com-
mon in the tropics, may cause a dysentery characterized

Pffv^

PF""'^

raj

p^i

^^L -'s^cfly^K ^

1 « 1

1 '*

1 ^i**»

Stages in the life of different types of the malarial protozoa growing
on and in red blood cells. Enlarged 1000 diameters. (From KoUe
& Wassermann.)

% s^

^ JrJ^

Protozoa called Leishman-Donovan bodies that were thought
to be sporozoa until they were grown in pure cultures
when they develo])ed flagellated forms like those in the
illustration, which placed them among the flagellates.
(After NicoUe.)

ANIMAL MICROBES OR PROTOZOA 241

by discharges of blood and mucus which may be fol-
lowed by abscesses of liver, lungs and brain. This patho-
genic form now goes by the name Endamoeba his-
tolj'tica, but it has many synonyms and its history is
all mixed up vrith. that of its supposedly harmless near
relative, Endamoeba coli. The nucleus is said to be so
different in these different forms that they can easily
be recognized by its characteristic appearance. And
the number of nuclei in the cysts is quoted as a dif-
ferential point. But it is disheartening to the lover of
the immutable to think how these two factors may vary.

We were able to show that several varieties of amoebas
obtained from the feces of different animals, includ-
ing man, all quoted as "free living" forms by experts —
that is, forms that grow onh' outside of the animal
body — are able to grow in pure cultures, feeding only
on fresh animal tissue placed in artificial media in test
tubes or Petri dishes. Such culture forms, growing
vigorously and continuously without bacteria on suc-
cessive transplants of this tissue medium, present ap-
pearances varying enormously in each strain with the
temperature at which they are allowed to grow, as well
as with other factors.

Fortunately, though we may not know what specific
name to call an amoeba when we see it in the feces, we
know what to do to prevent amcebic dysentery. We
must keep food and drink from fecal contamination,
which meanjs personally fly swatting and clean hands.
We must protect the water supply. Easy to say, but
how difficult to do! At least suspicious water can be
boiled and vegetables and fruits cooked, or washed
thoroughly and immersed in boihng water for ten
seconds.

242 WHO S WHO AMONG THE MICROBES

Then we have a cure, though with exceptions again.
Emetin in various forms and combinations has benefited
and even seemed to cure a number cf cases.

A few years ago great excitement prevailed among
the dental profession when two investigators an-
nounced that pyorrhoea, that dread of lovers of good
teeth, was due to an amoeba. We soon showed that the
poor amoeba wasn't to blame in this case, at least pri-
marily, if at all, though large numbers were found in
decaj'^ed and dirty teeth.

Some investigators now beheve that certain amoebas
may get into our joints and bones and cause symptoms
of arthritis, and this time their behef may prove to be
the truth, though we have yet no clear-cut evidence.

The next protozoan shown to be pathogenic for man
is the one causing that misnomer malaria (bad air).
What a discovery this was ! The Italian Laveran main-
tained in spite of much opposition and ridicule that
the minute amoeboid forms he had found in the red
blood cells of man during attacks of malaria were liv-
ing microbes and the cause of the disease. And after
his critical colleagues really studied the disputed forms,
they had to agree with him. He called his organism
Plasmodium malariae. Then they found that there were
three t3rpes of these protozoa that cause malaria. One
taking two days to develop is called the tertian type,
because the dreaded chill and fever come every third
day. The second form, taking three days to develop,
is called the quartan type, because the chill and fever
come every fourth day. Then there is the worst form
of all, or it may be a mixture of forms, the so-called
Estivo-autumnal or pernicious type, in which the chill
and fever may occur every day with irregular re-

AXIMAL MICROBES OR PROTOZOA 243

missions, or the infection may be so intense that the
victim may be struck down with dehrium followed by
coma and death in a very short time. This form may
affect some of its victims in other bad ways, producing
chronic disease and recurrences.

All of these bad forms still are active in the tropics
when the proper means of controlling them cannot
be carried out, but with the advance of public health
control the malarial parasites have practically disap-
peared from many parts of the world where they once
held sway.

Notwithstanding the fact that the wonderful
empjTic discover}^ in the eighteenth century of the
teUing effects of quinine on the disease caused by these
parasites was made long before the parasites were
brought into the hmehght, still, as late as fift}" years
ago the disease was common throughout much of the
world as well as in the tropics. What years of misery
it caused to many a hfe, young and old! What fan-
tastic ideas there were concerning its cause! Malaria
meant air from swamps, from damp places, from ex-
cavating ground, air that descended upon one at night
so that one carried an umbrella to ward off this falling
evil.

And then came the stunning demonstration by Man-
son and others of the fact, surmised long before by
the few as usual but not considered by the many, that
mosquitos carry the malaria germs ; that it was the
mosquito that rose from damp swampy places, that de-
scended upon us by night, that bit us freely in those
days when we had no fear of it except its disagreeable
effects ; it was this despised mosquito who was sho\^Ti
to be one of the mighty enemies that man must fight.

244 WHO S WHO AMONG THE MICROBES

And fight it he did with oil, draining away-
waste waters, with minnows and other enemies of the
larvae, with screening, and with treating and protecting
human cases. Now we in the Middle and Northern
States of the United States have practically no ma-
laria. The special mosquito carriers, the anopheles,
are seldom seen here at a glance.

In the meantime, mosquitos were studied all over
the world, and many curious facts were learned in
regard to the different varieties. The habits and dis-
tribution of the carriers of the malarial microbes be-
came very well known and many mysteries in regard to
malaria and the mosquito were cleared up.

Some of the differences between the "malarial mos-
quitos" (anopheles) and the more common harmless
varieties (culex) are shown in the illustration.

The first step in working out the wonderful cycle
of life of the malarial germ was made by MacCallum's
exciting discovery that there were sexual forms of these
organisms. Then Grassi and others worked out the
complete life cycle, showing that after infected blood
was imbibed by the mosquito the malarial male and
female germs fuse, then grow into a large body full
of little flagellated forms; these pass to the salivary
gland of the mosquito and from there they reach the
blood of a human being when the mosquito bites him.
When these small forms reach the blood cells of the
bitten human they round out into amceboid forms, grow
quite big and divide into a number of minute amoeboid
forms ready to infect new blood cells, or be imbibed by
another mosquito.

An organism that is considered a distant relative
of the malarial microbes was found in 1888 by Babes

Fig. 10
Chief compaeatite chabacteristics of Culex axd Anopheles.
(From Kolle and Hetsch.) Egg of Culex. 1, laid together in 'small

BOAT, THOSE OF ANOPHELES, 2. SEPARATE AND ROUNDED. LaRVA OF C, 3,
HANGS NEARLY AT RIGHT ANGLES TO WATER SURFACE, THOSE OF A., 4, ARE
PARALLEL TO SURFACE. BODY OF C, 5, WHEN RESTING IS HELD PARALLEL
TO WALL IN A CURVED POSITION, THAT OF A.^ 6, STANDS AT AN ANGLE OF
ABOUT 45° AND IS STRAIGHT ; WINliS OF C, 7, ARE GENERALLY NOT SPOTTED,
THOSE OF A., 8, ARE SPOTTED. In C. THE PALP^, 9, OF THE FEMALE ARE
VERY SHORT, OF THE MALE ARE LONGER THAN THE PROBOSCIS ; IN A., 10,
THE PROBOSCIS OF BOTH SEXES ABB ABOUT OF EQUAL LENGTH.

245

246 WHO S WHO AMONG THE MICROBES

in Rumanian cattle and independently by Theobald
Smith and Kilborne in cattle throughout Texas, suf-
fering from Texas fever. This microbe is now called
Babesia bigemina.

While this form has not been found to attack man,
it affects him indirectly, and an important fact in its
life history made its discovery of still greater prac-
tical worth to us. Smith and Kilborne showed in a
masterly piece of research work that the infection was
borne by a tick and transmitted to a new bovine by the
offspring of this tick. They demonstrated this some
time before Manson showed that the mosquitos carried
the malarial germ, so they were the first to direct our
attention to the important fact that lower animals may
be hosts or carriers of some of our microbe enemies.

Smith showed that if cattle were kept from infected
fields for two years and non-susceptible animals (horses
and mules) were allowed to feed there the bad ticks
might disappear. In the meantime, they showed that
ticks on animals might be killed by allowing the animal
to pass through an oil bath.

The serum from animals that have recovered from
Texas fever has been tried out for its preventive
quahties, but it has been found to be of little use.

Minute microbes like these Babesia have been found
in cattle in other parts of the world. A similar germ
has been found also in dogs in certain parts of the
world. This last variety has been studied exhaustively
by Nuttall and Graham Smith, but they didn't suc-
ceed in getting it to grow. Another variety has been
found in horses and still another variety in sheep. Each
variety seems to be able to infect only the one kind

ANIMAL MICROBES OR PROTOZOA 247

of animal, and each to be transmitted by one kind of
a tick.

There has been no more surprising discovery of
the cause of disease in man than that in the disease
known as tropical sleeping sickness. This is quite a
different disease from the one also known commonly
throughout a larger part of the world as sleeping
sickness, but whose real name is Encephahtis lethargica.
This one will be spoken of in the next chapter.

For years in the tropics many natives had been
attacked by gradually increasing weakness and somno-
lence, finally ending in death. The condition was rightly
called the sleeping sickness.

Then, just at the time Smith made his discovery of
the cause of Texas fever, Evans and a little later Lin-
guard found in the blood of horses in East India,
suffering from a wasting disease called surra, some
actively motile pecuHar flagellates hke those found
earlier by Lewis and others in the blood of about one
"v^ald rat in a hundred throughout the world, and Hke
those found so long before (1843) by Gruby in the
blood of a frog. Gruby had named his find trypano-
soma, which means a boring animal, because of the
appearance of a bore given by the fluted frill winding
about its body.

Neither the rat trypanosome nor the frog trypano-
some seemed to make its host sick. But in quick suc-
cession different investigators found in animals in
different parts of the country, each suffering from a
disease Hke surra, a similar boring-looking microbe,
and they proved by inoculation experiments that the
microbe reaUy causes the disease. In the midst of these

248 WHO S WHO AMONG THE MICROBES

discoveries Bruce found that a special biting fly, called
tse-tse fly, is instrumental in conveying the trypa-
nosome to another host.

No one had any idea that man was susceptible to
this kind of organisms.

Then one day Nepvieu (1898), while examining the
blood of some drooping natives in Africa to see if he
could find any malarial organisms there, saw the blood
cells being pushed about violently by some squirming
object. He watched it until he became convinced it was
one of those boring-looking trypanosomes. He found
a few more in several other cases; then Dutton and
Todd and others examined many of the natives and
found a few more. Finally, CastellanI found trypano-
somes in the centrifugahzed spinal fluid of twenty out
of thirty-four cases of definite sleeping sickness. His
work has since been fully corroborated. White visitors
in the country were also found to be susceptible. Vari-
ous species of biting bugs have been shown to be able
to transmit these microbes. The reason these striking-
looking fluted microbes were not seen before is chiefly
because so few are in the blood at any one time.

Novy and MacNeal in America were the first ones
to obtain a pure culture of this kind of microbe. They
made a soft medium of nutrient agar and rabbit's blood
and injected into it some of the blood from an infected
case. These blood parasites grew in the water of con-
densation, and continued to grow in successive trans-
plants in this artificial culture medium.

All of the harmful trypanosomes first discovered were
found chiefly in animals and natives of certain parts
of Africa, where they may cause terrible infections.
Later a variety was found to be causing much loss of

ANIMAL MICROBES OR PROTOZOA 249

life among cattle and horses in the Philippines. Then
Chargas found that a disease occurring cliiefly among
children in Brazil is caused by a peculiar kind of
trjrpanosome that passes part of its Hfe cycle in certain
of the tissue cells of its host, where it looks very like
the Leishman-Donovan bodies to be next described.

The symptoms caused by these trypanosomes are
similar in all of these conditions known collectively as
trypanosomiasis, or sleeping sickness. The victims have
irregular low fever ^-ith gradually developing emacia-
tion, tremors, incoordination, somnolence, coma and
then death; always the end was death. Now, with the
appHcation of the wonderful drugs that have been dis-
covered, the treatment of these conditions seems to
promise great results. Atoxyl, combinations of anti-
mony, and the latest and most hopeful drugs, a new
combination of arsenic sj'nthesized at the Rockefeller
Institute, and the Bayer 205, a patented German
drug, whose composition is not made public, seem to
be effective as cures in the first stages of the disease
in all of the forms except that occurring in Brazil,
where no drug seems yet to have any curative effect.

Another peculiar insidious, usually highly fatal, dis-
ease of the tropics called dum-dum fever, or kala-azar,
used to be considered a malarial cachexia. Then, in
1903, Leishman and Donovan independentl}^ found
some queer looking bodies ^Wthin certain of the spleen
cells of persons sick with this fever. Their discoverers
judged from the appearance and position of these
bodies that they were animal parasites and probably
the cause of the disease. Their judgment was found
to be correct. The bodies were known first as the
Leisliman-Donovan bodies. Later, when it was proved

250 WHO S WHO AMONG THE MICROBES

that they are really protozoa, they were given the
same name but in a scientific form, Leishmania
donovani.

That same year a native of Delhi arrived in this
country at Boston with what is known as a Delhi boil
or Oriental sore on his face. Wright examined this
and found it loaded with the same kind of bodies. Since
each of these microbes produces a disease so different
from the other, each is called by a different species
name. Wright's bodies are known as Leishmania
tropica.

The sand-fly is probably the chief culprit that trans-
mits these enemies.

Several interesting facts were brought out in at-
tempting to cultivate these microbes. No one at first
could get them to grow. Then Rogers, instead of put-
ting at blood heat all of his tubes containing bits of
infected tissue in Novy and MacNeal's culture medium,
left some at room temperature. When he examined
these he found evidences of growth. Some were di-
viding and some elongating. Not only that, but some
of the elongated forms began to wiggle, and behold!
there was a flagellum growing out from one end. So
they were flagellates, instead of being exclusively cell
parasites or sporozoa, as was first thought.

A combination of antimony has been found to be
almost a sure cure if given early enough in cases
infected with this type of microbe.

A number of protozoa, together mth many of the
bacteria, find the intestinal canal of man and lower
animals an ideal place for hving. Representatives of
all four of the large groups of protozoa may be found
there. Six kinds of amcebas, seven of flagellates, one

AXI3IAL MICROBES OR PROTOZOA 251

of sporozoa (coccidium) and one of the ciliates have
been reported as inhabiting man's intestinal canal from
time to time.^ Very Httle harm is done their hosts, ex-
cept by the amoebas.

But since some of these maj^ be at least the cause
of disagreeable diarrheas and might at most develop
more dangerous qualities, it is well to be on one's guard
against carriers and infected food, particularly in those
countries where these infections are more common.

*See Hegner on Intestinal Protozoa of Man, p. 660, in "Xewer
Knowledge of Bacteriology and Immunity," ed. by Jordan and Falk.
University of Chicago Press, 1928.

CHAPTER XIX
UNKNOWN MICROBES

FILTERABtE VIRUSES

Ultra-microbes, the smallest of all, the cause of yellow fever,
rabies, smallpox and a number of other diseases.

Here are mysteries for you! A whole group of dis-
eases exist due each to an infectious principle — a virus
that has not yet been identified as a microbe. As
many of these viruses in diluted suspensions pass more
or less readily through very fine porcelain or stone
filters, they are called filterable viruses. These filtrates
may look like clear Hmpid water and yet be very in-
fectious; that is, they may be capable of reproducing
the disease when injected into susceptible animals.
Examined under the liighest power microscope, no sig-
nificant formed particles can be seen. The filtrate,
therefore, contains either ultramicroscopic germs or
minute microbes with staining powers and refraction
so faint as to be non-demonstrable by knoTVTi methods.
Some idea of the immense numbers of investigations
made by research workers all over the world on diseases
due to such viruses may be obtained by reading the
symposium on this subject edited by Rivers.^

A list of sixty or more diseases is given by Rivers
that have been placed by different observers in this
filterable group. Many of these are diseases of plants

^ "Filterable Viruses." Ed. by Thomas M. Rivers. Williams & Wil-
kins Company, 1928.

252

UNKNOWN MICROBES 253

or of lower animals alone, so they may only affect
man indirectly. Fifteen of tliem have been reported as
infectious for man, most of them lightly and infre-
quently, a few severely and often. A number of these
affect both man and lower animals.

The process of filtration has played such an im-
portant part in the study of these viruses that we
should know sometliing about the kinds of filters used
and the way to use them. The process seems very sim-
ple, but in using the fine filters, especially, the filtra-
tion is much more complex than one would think.

The material composing the filter, the method of
manufacturing it, its thickness, the size of the pores,
the time filtration is continued, the pressure used, the
age of the filter, the preparation of the material to be
filtered, tests of filters and of filtrates, all are im-
portant factors to be taken into account in the de-
ductions we may draw from the results we obtain
through the process of filtration of these ultrami-
croscopic viruses.

As far back as 1884< Chamberlain, working at the
Pasteur Institute in Paris, showed that when he made
hollow candles of unglazed porcelain (finely ground
kaohn or hydrous aluminum silicate plus quartz sand
or siKca), closed at one end, the filter would retain
the bacteria of fluid cultures, but would allow certain
of their toxic products to pass through. It was found
later that porcelain filters ^^-ith different-sized pores
could be made, the finest allowing no known microbes
to pass, the next larger allowing the smallest bacteria
to pass, and the largest allowing all the known bac-
teria to pass. Similar filters were made in different
parts of the world.

254 WHO S WHO AMONG THE MICROBES

Then filters were made of diatomaceous or fossil
earth, now known as stone or Berkefield filters. These
were also made of different grades, distinguished by
letters N meaning normal, V coarse, and W fine or
dense. A number of firms have made similar filters
with different names, and of various sizes and thickness.

If a ground cross-section of any of these filters is
examined under the microscope it is seen to be made
up of granules surrounded by capillary spaces con-
nected irregularly by larger spaces or lacunae. The
larger spaces are more numerous in the coarser types.

Other filters are of asbestos disks devised by Seitz.
Then there are plaster of Paris filters and finally the
so-called ultra-filters made of collodion on a porous
support used chiefly for the separation of colloids.

When we once get our filters made, the first thing
we do is to wash them by forcing distilled water through
them. This rids them of any loose foreign matter. A
preliminary air test may then be done which, accord-
ing to the rate and size of bubbles arising under a
certain pressure, indicates either a gross defect or the
size of the pores.

Then the filters must be sterilized. This is usually
done by exposure to moist heat in an Arnold sterilizer
for several hours. Autoclave sterihzation must be used
with care, since there is danger of injuring the filter by
too great a heat.

After this the filter chosen for use is attached to
a pressure pump and is tested for its ability to hold
back certain known organisms of different sizes. It is
then ready for the material to be filtered.

This material is prepared in special ways accord-
ing to its character. If it contains any coarse particles,

UNKNOWN MICROBES 255

these should be removed by centrifuging or hj a pre-
liminary filtration through paper pulp or other coarse
filter. If it is thick, it must be greatly diluted. Its re-
action to hydrogen ion concentration must be deter-
mined.

Now comes the question of the effect of the filter
on the material being filtered. First there is the proba-
bihty of some of the material sticking to the sides
of the capillaries or of the filter walls. This adsorption,
as it is called, varies with the kind of material filtered
and the kind of material making up the filters. The
electric reaction of these materials (whether they are
electropositive or electronegative) makes a marked dif-
ference in the results, since porcelain, fossiliferous and
asbestos filters are negatively charged and plaster of
Paris filters are positively charged. Basic or alkahne
solutions are adsorbed by the walls of the first type
of filter, while acid solutions are not; the contrary is
true for the second type. But only the first part of
the fluid that passes through is adsorbed. When the
walls of the filter are covered with a film of the ad-
sorbed portion the fluid then comes through without
further adsorption.

To understand fully the mechanism of these reac-
tions one should know electro-physics. Practically, it
means that because of adsorption of the filtering ma-
terial by the pores of the filter we may not have the
same results in the first few centimeters of any filtrate
that we get with later amounts filtered.

The thickness of the walls of the filter of course also
influences the first filtrates coming through, as do also
the strength of the dilution and the kind of diluent
used in preparing the material to be filtered. The

256 WHO S WHO AMONG THE MICROBES

amount of deposit from the unfiltered material on the
surface of the filter also influences the rate and char-
acter of the flow through.

From this short sketch we see, as we said, that there
are many factors to consider before we can draw any
deductions as to the size and character of any virus
that may come through any filter. There is no ques-
tion that size is a most important factor, j^et organisms
larger than the estimated size of the pores of the
filter may appear in the filtrate. This may be due to
their plastic ability to mold themselves through spaces
othermse too small for them to pass through.

Recent workers stress the similarity of the virus
diseases, but this seems easy to overstress. We are
sure that among these sixty or more viruses listed by
Rivers, there is more diversity than similarity. In this
connection it is interesting to recall that scarlet fever,
wliich was early put with the virus diseases, is now
placed definitely with the streptococcal diseases, and
the virus of pleuro-pneumonia of cattle is just within
the hmits of visibihty. Then the kinds of tissue these
viruses attack and the whole course of the infection
caused by some are completely different from the
mode of attack and symptoms produced by others.
Thus smallpox virus attacks chiefly the skin and mu-
cous membranes, rabies virus chiefly the nerve tissue;
some, Hke smallpox, are extremely contagious, others,
like rabies and yellow fever, spread only by special
methods of inoculation.

One of the first diseases, if not the first, shown
to be due to a filterable virus is foot-and-mouth disease.

Any one traveling by automobile through Cahf ornia
or Texas during the summer of 1924! would not need

■■J

UNKNOWN MICROBES 257

to ask "What is foot and mouth disease." They would
know by some disagreeable experiences that it is a
highly infectious disease of cattle and other cloven-
footed animals, and that in order to help stamp it out
disinfection is practised on a large scale, including the
spraying of automobiles, camp outfits and other con-
tents of cars. In addition, they would find that em-
bargoes are laid on anytliing suspected of carrying the
infection into or out of the States infected.

Though it seldom attacks man and it can quickly
be controlled in animals, as the United States Depart-
ment of Agriculture reports show, wild rumors of the
extent of and danger from the disease caused much
fear and even hysteria among citizens and travelers.
Mohler ^ says that economic loss to the State of Cali-
fornia was about $7,000,000. Rumors of business fail-
ures were greatly exaggerated.

The origin of tliis 1924 CaUfornia outbreak was
traced to garbage from the Mare Island navy yard.
Presumably the virus was in some of the meat ob-
tained from foreign ports. Tliis garbage was fed to
a certain lot of hogs, who came down with such a hght
attack of the disease that it was unrecognized. The
hogs were sold into the county, where immediately
afterward the disease began to appear among the
cattle.

There is not a high mortality among the animals
affected, but they may be sick for some time. They
lose much flesh and weight, and their milk dries up.
The disease begins with fever, then little water blis-
ters appear chiefly on the mucous membrane of the

^ United States Department of Agriculture, Circular 400, 1926, p.
60.

268 WHOS WHO AMONG THE MICROBES

mouth, and on the skin between the toes and above the
hoofs. These rupture and form erosions and ulcera-
tions, which finally crust over and heal. The animal
seems to suffer pain and is lame while the disease is
in progress.

Only a few scattered epidemics have occurred in this
country, but the disease is common in Europe and in
some parts of Asia and South America. It has never
appeared in Australia or New Zealand.

That the virus is filterable was discovered acci-
dentally by Loeffler and Frosch in 1897. In order to
get from the vesicles a clear serum freed from cell
detritus they filtered it through a Berkefield filter.
What was their surprise to find that this clear filtrate,
when injected into cattle, caused the disease as readily
as did the unfiltered virus. They ruled out the possi-
bihty of the filtrate containing only a toxin by mak-
ing very high dilutions and injecting successive ani-
mals. No one has yet been able to cultivate this virus,
at least in such a way that others can corroborate
the work.

The second filterable virus discovered is the one
that causes mosaic disease of tobacco. Beijerinck made
the discovery in 1899. It has since been found that
the whole group of the mosaic diseases of plants are
caused by filterable viruses. Just how closely they are
related is not yet determined. They usually affect the
plant first by causing irregular blanching or yellowing
of the part attacked. This mottling may form a sort
of mosaic pattern, hence the name mosaic disease. In
certain of the diseases galls or enlargement of infected
areas may be produced. Certain unknown bodies in-
cluded in the cells of the plant have been described,

UNKNOWN MICROBES 259

which are thought by some to be the adult stage of
the inciting agent, but this has not been proved. Then
in the more poisonous types of virus groups of
the plant cells die. While many of the virus diseases
of plants cause heavy losses in commerce, others run a
comparatively mild course and do little damage. Kun-
kel ^ calls attention to the fact that a mild mosaic dis-
ease has increased the value of certain plants by adding
a variegated beauty to their foHage or flowers. Thus
the yellow leaves of certain abutilons and the variegated
flowers of some tulips are caused each by a mosaic
virus.

Diseased plants sometimes recover, and resistant
varieties may be cultivated. Insects carry the virus.
Spraying helps a little in their control. The best method
to do away with this pest, however, is to plant disease-
resistant varieties.

The next filterable virus demonstrated is a very
important one to man. It is the one causing that for-
mer dread of the tropics, yellow fever. It is no longer
a scourge since the epoch-making work of the American
commission in the Panama Zone not only demonstrated
so tellingly that its cause is a filterable virus, but
showed how it is conveyed and how it may be controlled.

The undiluted serum from cases of this disease was
shown by the commission in 1901 to contain a virus
that would pass through stone and porcelain filters.
The clear filtrate obtained was found to be infectious
for human beings who volunteered to allow themselves
to be used for test injections, since none of the lower
animals were known to be susceptible to this disease.

What bravery ! especially as there was no known cure

' In "Filterable Viruses." Ed. by Rivers — already quoted.

260 WHO S WHO AMONG THE MICROBES

for the disease. Some of them lost their Hves from
yellow fever in these telling demonstrations. That was
a thrilling piece of work they did. They further proved
that a certain kind of mosquito carried the virus, and
protection from it meant no yellow fever.

The wonderful improvement in living conditions as
a result of these demonstrations and the practical
application by Gorgas in. the Panama Canal Zone
proved brilliantly the enormous value to mankind of
the work and sacrifice of these investigators. The Canal
Zone was formerly a notorious yellow fever and ma-
larial district. The French commission had given up
work there because of the loss by death of 50,000 or
more workmen, chiefly through these two diseases. The
place was called the white man's grave. Then when the
American commission found out for certain that spe-
cial mosquitos are the dangerous transmitters of yellow
fever, as another type of mosquito had been shown to
be for the malarial microbes, ways of protection from
these pests were soon devised; and the practical ap-
pHcation of them by Gorgas and Guiteras was so
successful that hfe and work there were at last made
possible. The birthplace of Walter Reed, the head of
the American commission, is being made a national
monument in recognition of this conquest of yellow
fever. It must stand as a tribute to all who took part
in this monumental work, especially to Lazear, who
died, and also to Carroll and Agremonte, the other
members of this memorable commission, and to Moran
and Kissinger, who also volunteered for the service of
humanity — to all of these it must stand as a memorial.

A non-fatal but temporarily disabling disease re-
sembling yellow fever somewhat is dengue or breakbone

UNKNOWN MICROBES 261

fever. This was shown by Craig and Washburn to
be filterable and to be carried by the same kind of
mosquito as that carrying yellow fever. Last summer
quite a severe and extensive epidemic of this disease
broke out in Greece, wliich interfered with business and
travel.

The next filterable virus found is the one causing
a disease wliich might be said to be spread chiefly
through the sentimentality of people. This is that much
discussed but little understood disease called rabies or
hydrophobia.

The dog is the animal in wliich tliis virus is most
commonly found. Though other animals are susceptible
to it, the dog is the practical carrier. We have long
made this cry our slogan for the prevention of rabies,
"No stray dogs, no rabies," but we still have stray
dogs even in the most civilized countries, and we still
have rabies.

Indeed, some of the wealthiest (unfortunately wealth
does not always mean intelligence) communities seem
to have the most sentimentahsts, who beheve that noth-
ing should interfere with the hbertj' — should say, hb-
erties — of that noble friend of man, the dog. This
would be more reasonable if there were not so many
dogs throughout the land that run at their own sweet
will, and if they happen to have been bitten by a rabid
animal, they in turn may bite man, dogs or other
animals.

Many people say, "TV^hy all this hue and cry about
rabies?" We have seen a number of persons bitten by
dogs, even by dogs said to be mad, and these persons,
though they had no treatment, did not come do'^Ti
with rabies. We answer, "It is true that cases of hu-

262 WHO S WHO AMONG THE MICROBES

man rabies rather seldom occur after the bite of a
dog." This is due chiefly to two reasons.

First, only a small percentage of biting dogs are
mad ; though in the last two years this percentage has
increased materially. Thus, about one half of the 94<2
dead dogs sent to our Health Department laboratories
during 1927 for diagnosis gave evidence of having died
of rabies. Two years ago only eighty-five of the 360
dogs sent to us had died of rabies — a 100 per cent, in-
crease of the proportion of dogs mad, and 500 per
cent, of the actual number of mad dogs sent to us
for diagnosis. Of course, there are many non-suspected
biting dogs that do not reach our laboratories, so the
total percentage of rabid dogs among biting dogs still
remains small.

The second reason why we see so few human rabies
cases after a dog bite is that human beings are not
very susceptible to rabies, and so only a comparatively
few come down with the disease after a mad-dog bite,
even if they take no treatment. It is estimated that on
an average only about 10 per cent, of humans bitten
by mad dogs and untreated develop rabies. This is
not a very great risk to incur. Of course, this is only
an average percentage. Those people develop the dis-
ease more readily who are bitten on parts near the
brain — ^that is, about the head — especially the face,
and on other parts well supplied with nerves, such as
the tips of the fingers. On the other hand, we know
that people who take the Pasteur preventive vaccine
immediately after having been bitten by a mad dog
run on the average only a 0.1 per cent, risk of de-
veloping the disease. In other words, if you don't take
the specific treatment you run 100 times a greater

UNKNOWN MICROBES 263

chance of having rabies than if 5'ou do. It's up to
you to choose. Most people choose to take the treatment.

For, once a case begins to show symptoms, we see
a sight that we may never forget. The convulsed vic-
tims present a terrible appearance. At this stage there
is no known cure for the disease. The same fatal out-
come occurs in dogs, so that those who truly love
mankind and dogs and are informed are eager to stop
the disease.

The virus was shown by Remlenger, in 1903, to pass
readily through the finest filters. The virus from
the salivary glands is more filterable than that from
the brain.

The virus, after it enters a wound, passes up the
ners'es and multipKes exceedingly in the central ner-
vous system. It also develops in the large nerve cells
of the saHvary glands. It may be demonstrated in the
sputum of infected animals before any symptoms of
rabies appear.

As soon as the virus reaches the brain pecuhar bodies
appear in the large nerve cells. These cell inclusions
are commonly called "Negri bodies," after the one
who first published their discover3\ One of the authors
discovered these bodies at the same time independently
and with Lowden made extensive studies of their na-
ture. The conclusion was reached that these bodies
are one form of the specific cause of rabies, and Wil-
liams gave them a scientific name which is long enough
to forget. The practical point about these bodies is that
they are diagnostic of rabies. We have developed a
quick method of demonstrating them which is now
used in all the laboratories of the world. These bodies
only show well by this method if the brain is fresh;

264. WHO S WHO AMONG THE MICROBES

therefore, an animal suspected of having died of rabies
must be taken to the laboratory immediately if the
best results are to be obtained.

All of the anxiety due to the fear of rabies, and all
of the discomfort and inconvenience in taking the many
injections of the otherwise wonderful Pasteur vaccine
treatment, may be avoided by the simple and rational
expedient of having no stray dogs. Cats are usually
not dangerous, because while they are very susceptible
to rabies they nearly always have what is called dumb
rabies; that is, they become gradually paralyzed and
die without biting any one. So, while we should be on
our guard against the occasional cat that may develop
the furious form of rabies, our slogan, which we reit-
erate, "No stray dogs, no rabies," is true in practice.

The recent increase in rabies in New York City and
in many parts of the United States is due chiefly to
the fact that people have been too sentimental or too
careless to check the wanderings at large of their canine
friends. They don't seem to reahze that they confer
a benefit on all dogs, as well as on people, by keeping
their own dogs under control.

Now we come to a virus that causes a disease dreaded
because it so often leaves its victim lame for Hfe.
This is the virus causing infantile paralysis or poli-
omyehtis. The word infantile tells the story of where
we find the greatest number of affected ones. Again
we have a mystery that, notwithstanding innumerable
investigations, remains unsolved. We don't even know
how wide-spread the virus is. An occasional case occurs
in almost any part of the country, a few more in
the temperate zones, and then a small epidemic breaks
out hke the one around Boston in 1928.

UNKNOTTX MICEOBES 265

People can't be very susceptible to this disease be-
cause there are so comparatively few cases. Even in
the largest epidemics only about 4 per cent, of the
population are attacked. Cher 80 per cent, of these
have been cliildren. ^lore grown-up people are affected
in the country districts. Tliis is probably due to the
fact that city people, as a whole, especially among
the poorer classes, when infected, get the disease lightly
if at all because they are a httle immune. ^Moreover,
they may not have the lasting lameness which so often
follows the paralysis that develops in severe cases. With
proper treatment much lameness can be avoided.

Human convalescent seriun is supposed to have an
inhibiting effect if given early enough. But early diag-
noses are difficult to make, and not all cases respond.
Many research workers are intensely studying this
disease now. Due to the interest and generosity of Mr.
Jeremiah !Milbank, a large fund makes possible these
studies in different parts of the country. This virus
does not pass through our fine filters readily.

Another of these less readily filterable viruses is
that causing measles. Yes, this disease so common, so
definitely characteristic with its regular invasive period,
its well-marked symptoms and its practically lasting
immunity, must still be classed with those of unknown
etiology, though a few in"estigators have tried to make
us beheve otherwise. One of these ubiquitous strepto-
cocci has been brought forward as the culprit, but
we haven't yet been able to find enough e^^dence to
con%'ict it.

We are just through another measles year in New
York City. What does "measles year" mean.? you may
ask. It means that every other year for the past ten

266 WHO S WHO AMONG THE MICROBES

years we have had tens of thousands of cases of measles
in this city, while during the alternate years there have
been only thousands.

This seasonal variation, as some of you know, is due
to the fact that measles, being very contagious, once
started, spreads quickly through a community. All
those who are susceptible and who come in contact
with a case contract the disease in rapid succession.
Then it takes about two years for a new group of
children to become old enough to run about and so
to increase the number of those who may communicate
the disease. Of course, in different sections of the coun-
try this weeding out of susceptibles may occur more
irregularly and at different year periods. Even in New
York City the present regularity may not continue,
but it has certainly been very marked during these last
ten years.

The most important fact in relation to these sus-
ceptible cases is that in the very young children — under
three years old — measles predisposes to a pneumonia
which frequently ends with death. The older children
do not often develop pneumonia. They pass through the
disease usually with no bad effects. The chief cry,
therefore, concerning measles, is "What can we do
to prevent it in the very young.'"' Mothers exclaim,
"Have you not a senrni or a vaccine that can be used
to prevent this disease, like the serums and vaccines
that have done so much good work in the prevention
of smallpox, diphtheria, lockjaw, scarlet fever, rabies
and other diseases?"

We have to answer "No," we have no manufactured
vaccine or serum for it. While we have no universally
accepted serum stimulated in animals by the action of

UNKNOWN MICROBES 267

a knowTi germ to cure this disease, we have a serum
that has a very marked action in preventing it. This
serum is called convalescent serum. It is obtained from
the blood of human beings who have recovered from
measles.

The first doctor who decided to use such blood had
reasoned that as those who had had an attack of measles
usually never had another attack, the blood of such
people should contain an antibody against the virus,
and that such blood, if injected into those who were
just coming down 'w^th the disease, might cure them
or at least prevent them from having a severe case and
getting pneumonia. So he collected what blood he could
from those adults who had had measles and were wilHng
to give their blood, and after testing it for its purity, he
injected a number of patients with it. The good results
were marked, but as he was unable to obtain much blood
at a time he could not make a demonstration of its
efficiency striking enough to cause the medical pro-
fession of the world to take notice. Occasionally fol-
lowing him a doctor would use what httle blood he could
collect and report favorably on its use. The chief trou-
ble was the difficulty of getting enough blood of known
potency to have the desired effect. Then about three
year ago, one of us had a wonderful opportunity to get
a large quantity of this measles convalescent blood.

Quite an extensive epidemic of measles occurred in
a southern university where many of the students
coming from rural districts had not had measles. These
students volunteered in large numbers to give their
blood during convalescence. So we sent one of our
doctors down there with a trunk full of sterile bottles
and other apparatus for drawing and collecting the

£68 WHOS WHO AMONG THE MICROBES

blood. At first only the boys were tapped, but when
the girls objected that it was unfair they were in-
cluded. In this way large quantities of blood were
drawn at different periods of convalescence. With tliis
we were able to find out definitely later the best time
to draw the blood after the person had recovered from
the disease. This time, they found, was from ten days
to three months after recovery. With tliis blood serum
we were able to treat nearly 2000 children during the
measles year of 1926. The dose is from five to ten cc.
And they were able to show very clearly that such
blood serum had a marked effect in protecting from
measles if given early enough, or in modifying the
course of measles if given later. Even j^ears after
an attack of measles, a considerable amount of anti-
body remains in the blood, but of this the dose is at least
six times as much.

The next important virus classed with the filterable
ones is that destroyer of beauty, the smallpox virus.
This too, like measles virus, passes with difficulty
through only the coarser stone filters. And this too
is a definite disease with characteristic symptoms. But
it has an advantage over measles from the standpoint
of studying it, in that it can infect certain lower ani-
mals with its characteristic lesions. Furthermore, we
have the innocuous co\s^ox virus which we can study
and from which we can make an efficient vaccine
against the deadly smallpox virus.

Nothwithstanding all these aids to study, we still
don't know what kind of a microbe the smallpox germ
is. As in the diseases produced by so many of these
filterable viruses, we find certain cell inclusions in the
epithelial cells of the pustules formed all over the skin

UXKXOTTX MICROBES S69

of the sufferer, which some of us have thought might
be the specific microbes. But we haven't been able to
grow them and we haven't been able to recognize a
clean-cut resemblance to any known microbes. So we
call them Guaniari bodies, after the one who first
wrote about them, and let them go at that.

The number of the descriptions of these forms and
the long and complex Hfe cycles given to them by some
of our protozoologists ought to make us sure of their
nature ; but no, we are just as uncertain as ever.

We are certain of one thing, however; that is, that
the bovine vaccine is a powerful preventive of small-
pox, and that those who don't use it in the countries
where they are not forced to are extremely ignorant
and foohsh.

Among the other diseases declared to be due to fil-
terable \'iruses there are not any of great general im-
portance to man. Mumps, certain common colds, cer-
tain cases of grippe, among them, it is true, may be
considered as decidedly disturbing at times, but they
haven't the big importance that most of the other dis-
eases cited have.

Then come the Rickettsia, those pecuhar masses of
irregular granules described first by Ricketts in typhus
fever, that only gradually after long study by Wolbach
and others are being accepted as probable micro-
organisms. They are found in Rocky Mountain spotted
fever, trench fever, heart water disease and flood
fever. They have all been traced through ticks, body
hce or bedbugs as carriers. If these pests of the unclean
can be prevented, such diseases cease. It is thought that
typhus may also be carried directh'. But in the World
War it was practically shown that if troops were pro-

270 WHOS WHO AMONG THE MICROBES

tected against vermin, neither typhus nor trench fever
developed. It was not so many years ago that body
hce traveled around freely over the tenants of the tene-
ments of the world. We had typhus in New York. Then,
with the disappearing of the lice, a mild type of typhus
appeared, and now, with the lice gone (shall we say?),
we have practically no cases of this type of disease.
While we don't know the cause of typhus (we can't
grow the Rickettsia bodies), it has been found that a
certain bacterium belonging to the proteus group, iso-
lated from typhus cases, agglutinates in the serum of
any case that has typhus. We don't know why. It is
simply used as diagnostic test.

That most perplexing of diseases known officially
as epidemic encephahtis and commonly as sleeping sick-
ness (number two) is an appropriate one to occupy
the final place in this list of diseases of unknown origin.
For we have no idea of its cause. Dr. Neal has recently
summarized the little we know about it. The following
are excerpts from her articles : *

The earliest recognized cases in the present outbreak of
the disease now known as epidemic encephalitis were de-
scribed by Cruchet, Moutier and Calmette in 1917. . . .

During the past ten years an enormous amount of work
has been done by scientists in many countries to determine
the cause of this disease, so protean in its clinical manifes-
tations and so terrible in its chronic effects. . . .

The early conception that it was due to botulism or
that it was an atypical form of poliomyelitis has been
sufficiently disproved to be dismissed. . . .

There has been much discussion both for and against
a relationship between influenza and epidemic encephalitis.

*Neal, "Present Status of Etiology of Epidemic Encephalitis,"
"Jour, of Am. Med. Assoc.," Vol. 91, p. 39, 1928.

UNKNOWN MICROBES 271

This has been based on the more or less coincidental ap-
pearance of these two diseases in many places in the recent
outbreak ; on the possibility of the same relationship as to
time having occurred in the past, and on the functional or
organic disturbances of the central nervous system some-
times occurring with or following in the wake of attacks of
clinical influenza in individuals. In view of the lack of
knowledge concerning the cause of influenza, all the discus-
sion seems to be of an academic rather than of a scientific
nature. . , .

There are three theories which assume that: (1) it is
a toxic disturbance of the central nervous system due to :
(a) Toxins produced by organisms located probably in
the respiratory or gastro-intestinal tract, (b) Toxins
elaborated as the result of metabolic disturbances. (2) It
is caused by cultivable bacteria. (3) It is caused by a
filterable virus. . . .

The case for the toxic origin of epidemic encephalitis
does not seem to rest on a very firm foundation. Many
points of evidence in regard to liver lesions, for example,
are not corroborated by other workers or are differently
interpreted by them. Moreover, the manner in which
the disease spreads in increasing numbers from place to
place and since subsided strongly suggests that it is of
an epidemic nature. In its epidemiologic manifestations it
bears a strong resemblance to poliomyelitis and to menin-
gococcus meningitis. Therefore, if one assumes that it is
of d toxic nature, one is forced to hypothesize some infec-
tious disease that was prevalent in diff'erent parts of the
world for some years to the eff"ects of which epidemic
encephalitis was due.

The evidence in favor of a known bacterial cause is
slight. That it is due to a filterable virus is considered
probable, but even here the evidence is not clear cut.
We are therefore forced to conclude that up to the
present time the causal agent of epidemic encephahtis
has not been made manifest.

CHAPTER XX

MAN MAKING USE OF HIS ACQUAINTANCE
WITH MICROBES TO PROTECT HIMSELF

A SUMMARY

Clean milk — Clean water — Clean food in general — Protection
against disease germs and disease carriers.

In the foregoing chapters we have attempted to give
as clear an idea as possible in such a small compass of
how microbes came to be known, of how they hve, of
their helpful and harmful effects on man and of how
man has learned in some measure to control and use
them.

As we have intimated, long before microbes were dis-
covered man tried to make his life safer and more com-
fortable by employing certain methods that, unknown
to him, depended upon the control or use of microbic
growth for their successful working. The origins of
many of these early uses are lost in antiquity.

The drying, pickling and freezing of meats and
fish, the souring of milk, the making of wines, the ret-
ting of flax, and so on, all began to be used so early
that their beginnings are mixed up with myth and
tradition. Bacchus the Greek god of wane, Osiris the
Egyptian god of brewing, and various other gods are
illustrations of the kind of explanations given of the
originators of many customs.

Even after some definite knowledge had been ob-

272

USE OF ACQUAINTANCE AVITH MICROBES 273

tained concerning microbes and their relation to dis-
ease, the great majority of physicians and sanitarians
put emphasis on things which had httle importance so
far as the development of communicable diseases was
concerned. The atmosphere was thought to have much
to do with conveying the disease-producing germs, and
filth was believed to be the frequent soil for their
propagation.

One of the writers remembers as a student at Co-
lumbia University hearing Professor Chandler giving
an illustrated lecture on sanitation. A series of pictures
illustrated the deadly nature of sewer gas. For in-
stance, the sewer received the throat discharges from a
child sick with diphtheria. The diphtheria baciUi grew
in the filth and in some remarkable way gained ac-
cess to the sewer air, spread through the sewer, trav-
eled up the house drainage pipe of a neighboring house
and finally passed through a hole in the pipe into the
air of a room and were there inhaled by a sleeping
child. The unfortunate child contracted diphtheria
and, according to Dr. Chandler, died from it. We now
know that very few disease bacteria continue to thrive
in sewage, and that sewer air and house drain air,
though odoriferous, contain no sewage microbes, since
these germs cannot escape from the fluid sewage hold-
ing them.

Until very recently it seemed almost evident that
microbes of diseases Hke malaria traveled by the air
route and infected persons passing through infected
regions. Now we know that the spread of infection
among human beings is due to the mosquito that be-
comes infected from a human case and then bites other
humans and so inoculates them with the malarial germs.

274 WHO S WHO AMONG THE MICROBES

Well into the present century it was believed by a
number of sanitarians that many disease-producing
microbes, as well as the spore-bearing bacilli, develop
in the soil and in decomposing animal and vegetable
matter. They thought that increased rain causes the
ground water to rise to the upper contaminated surface
soil so to become infected and later to infect surface
water supphes, wells and springs. The same ideas
caused great attention to be given to getting rid of
nuisances and filth in time of threatened epidemics.
Now we know that healthy human carriers of the germs
of typhoid fever, cholera, diphtheria, scarlet fever and
many other communicable diseases were the usual
spreaders of infection, and that the soil and dirt were
not in themselves carriers except temporaril}^, as they
were contaminated by careless or uncontrolled human
or other animal carriers.

It takes a great deal of good judgment and knowl-
edge properly to evaluate the importance of cleanli-
ness as a measure of insuring health. No intelligent
person would consider the httering up of the streets
with loose newspapers and discarded banana skins as
a serious menace to health, while all would agree that
the consumptive that expectorates freely on the pave-
ments of the street is a menace.

Milk is par excellence a food material suitable for
the growth and multiplication of disease microbes, espe-
cially the typhoid and scarlet fever germs. Occasionally
in custards, jellies, fresh meats and canned goods that
are not protected certain pathogenic varieties of germs
may continue to grow and increase, but in materials
containing insufficient or inadequate food elements for
these microbes, such as water, dust, decomposing leaves

USE OF ACQUAINTANCE WITH MICROBES 275

and the like, they may exist for a while if deposited
upon them, but they do not multiply and after a
time they die. The fact that microbes are invisible to
unaided eyesight makes it impossible for the ordinary
observer to be sure when and where infection may lurk,
so that the endeavor to secure cleanliness in the per-
son, in the home and in the town or city not onlj^ aids
happiness but also health, because in remoA^ng much
harmless dirt we also frequently remove dangerous
microbes ; in removing broken crockery, tins and any
receptacle that may catch the rain-water, we prevent
breeding places for mosquitos, and in keeping our
kitchens and households clean we prevent the develop-
ment of flies and other insects which may become
carriers of disease microbes.

Thus cleanhness is a great safeguard, not so much
because it removes breeding-places for microbes, but be-
cause in disposing of the waste we also remove any
human disease germs which may have been added to it
and make it impossible for the development of insects
which may mechanically or as intermediate hosts spread
infection.

The attention of those fighting communicable dis-
eases has been more and more focused on the location
of the disease in human beings and therefore the prob-
able path of exit of the germs, the length of time
during convalescence the germs persist and may be
communicated to others, the existence of healthy car-
riers of the disease-producing microbes and the dura-
tion of the resistance of the microbes to drying, sun-
light, heat and chemicals. The germs attacking the
food-producing or man-serving animals have been in-
vestigated in the same way both with the idea of pre-

276 WHO S WHO AMONG THE MICROBES

serving the animals for man's uses and of making life
more desirable for themselves. In the few instances in
which animals transfer communicable diseases to man
the methods by which the infection is communicated
have been especially carefully investigated.

The water, milk and food supplies have been studied
so as to apply methods of preventing them from be-
coming infected with dangerous germs, or, when that
has seemed to be impossible, to use methods that destroy
the infection by heat or disinfectants.

The progress made toward victory by man against
the individual microbes already described Is well il-
lustrated by his fight against typhoid fever. The dis-
covery of the typhoid bacillus as the cause of typhoid
fever was in our hands the key to unlock the mystery
of its transmission. Examination of the stools of pa-
tients sick with disease proved that the typhoid germs
passed with the bowel movements. Then came the sur-
prising discovery that about 2 per cent, of the per-
sons suffering from the disease contract a chronic
typhoid germ infection of the gall bladder which makes
these persons as dangerous as are typhoid fever pa-
tients. These facts brought about revolutionary changes
in our preventive measures to render water, milk and
other food products safe. It was found that any typhoid
bacilli gaining access to the milk actually multiply in
it, while those contaminating the water supply not only
do not multiply in the water but gradually die. The
interesting fact was noted that their period of existence
is only a few days in polluted waters, but several weeks
In otherwise pure water. The polluted waters contain
substances inimicable to the germs.

Let us look for a moment first at the present sani-

USE OF ACQUAINTANCE WITH MICROBES 277

tary methods of handling the milk situation. Raw
milk is now allowed to be sold in cities only when it is
produced under almost ideal conditions. Those who
wish to be employed in the dairy who are to have any
contact with the milk are first questioned as to whether
they have ever had typhoid fever. If the answer is "yes"
they are not accepted. If they are accepted, they submit
to blood tests which will generally indicate whether
they are typhoid carriers or not. To make assurance
doubly sure, their stools are subjected to bacterial tests.
The employees are also frequently examined by physi-
cians as an additional safeguard. These conditions are
so difficult to carry out that the bulk of the milk
consumed in cities and towns and much of it in the
country and even on farms is now heated sufficiently
to kill the typhoid bacilh before it is consumed. An
immense amount of investigation and experimentation
has been done to establish rules for pasteurization. Since
milk is one of the best of foods for all ages, it was de-
sirable not to injure the food value, taste or appearance
of the milk. Otherwise it would not be as nutritious or
tasty. It was found that temperatures above 145° F. in-
jured the httle fat globules encased in the protein films,
so that cream did not rise as well or seem as thick.
Fortunately, it developed that an exposure of the bac-
teria in the milk for twenty minutes to a temperature
of 140° F. was sufficient to kill all disease bacteria apt
to be in milk. There remained then to study the pas-
teurizing machines in use to discover what were the ir-
regularities in the rate of flow and in the temperature
in different parts of the machines and to what degree
these could be remedied. It was found that if we placed
the minimum required temperature for holding the milk

278 WHOS WHO AMONG THE MICROBES

at 143.5 and the time at thirty minutes we had a suf-
ficient margin of safety. A code has just been adopted
by the Federal Pubhc Health Service, which will be
submitted to the different States and cities, which if
adopted and carried out will make pasteurized milk
practically safe.

The next great source of human infection was the
typhoid bacilli carried to man by means of the water
he drank. Until recent times the water of streams and
of shallow wells was consumed thoughtlessly by the
great majority of people. In populated districts the re-
sult was disastrous. The typhoid patient or the inno-
cent typhoid bacillus carrier, knowing nothing about
the danger to others, deposited his infected fecal mat-
ter in some privy on the side of a brook or near a well.
Some of this would leak into the brook or well, or per-
haps a heavy shower would develop and the stream
would rise, flow into the privy and sweep out the ty-
phoid bacillus infected material into the brook and so
into the reservoir, and from there finally to the city
water main and to the people drinking the water.

The first attempt to remedy these evils was through
filtration of the cities' water supply and the removal
of privies from dangerous places. These improvements
made a remarkable difference in the typhoid toll. Filtra-
tion plants, however, are costly and need expert opera-
tion. They were not practical for small places. Even
in the plants of large cities at times something went
wrong with the filter plants and sewage escaped into
the drinking-water. Fortunately, it was then discovered
that a small amount of chlorine could safely be added
to the water. When the water was collected from the
country-side or from the mountains and had little or-

USE OF ACQUAINTANCE WITH MICROBES 279

ganic matter, even one part in a million of chlorine
would kill any typhoid or other germs which are liable
to cause human disease. When the water was more
turbid or contained organic matter from more densely
inhabited regions as much as one part in a hundred
thousand became necessary. Within a few hours after
its use the chlorine becomes united to the organic mat-
ter, including any microbes, and makes compounds
which are absolutely harmless. At the present time fully
80 per cent, of all the water consumed in towTis and
cities has chlorine added. When the larger amounts are
put in there is sometimes a rather disagreeable taste,
but otherwise the water is harmless.

The third means by which tj^hoid fever is spread
beyond the confines of a family where a typhoid case
exists is through shellfish. Oysters naturally grow on
the shores of the ocean or in the bays in which the
water is not quite as salt. The bays are far more con-
venient for the cultivation of oysters. In time cities
encroach on these bays, and the oystermen feel that
as they were there first it is not their business to move
but it is the business of the city to take care of its
waste. This brings about frequently a condition in which
oysters are being raised in polluted waters, and if they
become infected they remain so for a number of weeks.
When the oysters begin to die they form a splendid
soil for the growth of the typhoid bacillus. Until the
health authorities of the Federal Government and of
States and cities took over the control of the osyter
industry quite a number of outbreaks due to oysters
developed. A few years ago in New York City hundreds
of persons developed the disease before it was traced
to the oysters. At the present time the safeguards are

280 WHO S WHO AMONG THE MICROBES

SO great that there is very little danger. Shellfish are
safer during the cold seasons of the year, because when
the water becomes cold they hibernate and during this
period they drink almost no water, so that even when
they lie in polluted water they are comparatively safe.
Oysters when fried or stewed are safe, as the heat is
sufficient to destroy the typhoid bacilli.

Owing to these safeguards which have been thrown
about our milk and our water and our shellfish, there
is very Httle danger of contracting typhoid fever in
cities where the health authorities are active, except for
the occasional careless carrier that may elude their vigi-
lance. This has brought about the fact that the develop-
ment of typhoid fever in the last fifty years has de-
creased one fifteenth of what it formerly was. When the
occasional case or carrier does occur the members of
the household must use extreme precautions to prevent
the contracting of infection through personal contact.
Hands and utensils must be kept scrupulously clean,
and all fecal and other discharges must be carefully re-
moved and sterihzed.

When the writers graduated from their medical
schools, the wards of the hospitals w^ere filled in the
late summer and autumn with typhoid patients. Now
with the control that man exercises over the trans-
mission of their cause, these cases are decidedly rarer
and students eagerly seek to examine and study any
cases that occur. There are times and places where good
control of food and water is impossible. During wars,
for instance, the troops frequently must live under most
unsanitary conditions. Until the most recent wars, the
loss from tjnphoid fever and dysentery was almost as
great as from injuries. Again, in isolated country places

Counting colonies grown from dilutions of samples of the city's
milk supply

Corner of laboratory for bacteriological examination of milk

>'2
'2 =2

— ■■n

V. _

USE OF ACQUAINTANCE WITH MICROBES 281

and in uncivilized countries one is in danger of infec-
tion. For these conditions we resort to inoculation with
typhoid vaccine, which is a suspension of dead typhoid
bacilli. This gives great but not absolute protection for
two years.

Somewhat similar means have cut down the distress-
ing summer mortality from the diarrheal diseases of in-
fants which we have learned were partly due to mi-
crobes. For many years the children and especially the
infants in cities suffered from serious attacks of di-
arrhea whenever the heat and humidity were great.
Sometimes during a very hot spell many hundreds of
children and at times even thousands would die from
the effects of such diarrheas.

Nearly thirty years ago while we were experimenting
upon different diets for kittens, we found that those fed
on raw milk developed diarrhea from it. In examining
the milk we found it teeming with bacteria. This led to
an investigation and we found that the milk coming in
on short hauls was delivered warm into freight cars and
there remained for hours before being shipped to the
city. No ice was applied. The production of milk at
that time was not under the safeguards now employed.
The knowledge gained by this investigation started us
to make a definite study as to what relation the milk
bacteria and the changes caused by their growth in
the milk had to the diarrheas of infants. The next sum-
mer, through a number of physicians, we selected some
hundreds of infants who were less than six months of
age. Those who were fed by their mothers were left on
the mother's milk ; those who were fed on condensed milk
were left on that food. Those, and these were the ma-
jority, that were fed on store milk were divided into

282 WHO S WHO AMONG THE MICROBES

three groups. One was left on the store milk, one was
given good pasteurized milk and the rest were given the
very best of raw milk, which we now call certified milk.
These infants were watched by physicians and nurses
during the summer. When an infant became ill it was
taken off the milk and given the proper treatment.
It was found that the babies on the breast milk thrived
the best of all; then those on the clean raw milk and
on the good pasteurized milk. Far behind them came
the babies fed on the loose grocery milk. This last milk
on examination was found to have millions of bacteria
in each teaspoonful before it was heated at the homes.
This showed that the cheap store milk teeming with
bacteria had developed sufiicient changes because of
the bacteria to be harmful to infants and to cause
diarrhea. On older children it had little or no harmful
effect. The same experiment was tried again in the
winter months, and to our surprise there was not a
great difference between the results of feeding infants
the different kinds of milk. The breast milk still gave
the best results and the loose grocery milk somewhat
poorer results, but very little diarrhea developed. When
this investigation was completed we consulted with Dr.
Holt, the famous pediatrician. After studying the ma-
terial together we came to the conclusion that diarrheas
in summer were due to several tilings. First, even cow's
milk modified is not the equal of human milk as food
for human infants. Second, cow's milk which has be-
come contaminated with an excessive bacterial growth is
distinctly harmful. Third, that careful supervision by a
physician or nurse of the cleanhness of the baby, of the
proper clothing of the baby, of the proper ventilation
of the baby's room and the proper care of a baby dur-

USE OF ACQUAINTANCE WITH MICROBES 283

ing an attack of diarrhea was of great value. These
investigations were really the starting point for the
modern control of the milk supply. With the develop-
ment of baby health stations, the production of clean,
well cared for milk, and the education of parents as
well as physicians, severe summer diarrheas have prac-
tically ceased to develop. Instead of the mortality in
summer mounting during the hot months owing to the
deaths of little children, the mortality remains low and
the intestinal diseases are a minor factor. The bacteria
were shown to be the exciting factor of the diarrhea,
but the}^ were aided by the lowered resistance brought
about by the summer heat, by improper food and im-
proper care.

The question of tuberculosis in infants due to milk
has received much attention. Tuberculosis is a preva-
lent disease among not only human beings but among
cattle. It is now knowTi that the tubercle bacilli in cow's
milk produce infection in little children which may be
fatal in character. In older cliildren who have some
immunity the bacilli are less deadly and only make local
lesions. In adults they are practically harmless. We are
able to prevent the spread of tuberculosis in infants and
young children either by pasteurizing the milk or by
freeing the herds of infected cattle discovered by means
of the tubercuhn test. This test is used in two ways.
In one way an injection is made under the skin of the
animal with a small amount of tuberculin. The temper-
ature of an infected cow begins to rise at about the
twelfth hour and reaches its height four to six hours
later. It then slowly subsides. This infected cow is re-
moved from the herd. The other test is what we call
the intracutaneous test. A tiny amount of tubercuhn

284 WHO S WHO AMONG THE MICROBES

is injected through a hypodermic needle into the skin
or it is rubbed into a scratch made along the skin. In
about 12 to 24 hours a papular elevation develops with
redness extending about one tliird of an inch about the
point of injection or on each side of the scratch. This
positive reaction condemns the cow. When either of
these precautionary measures is taken, milk is safe for
use by infants and children. The advantage of using the
tuberculin test is that by weeding out diseased animals
the other cattle are protected from infection.

Besides tuberculosis and typhoid fever, that bad con-
dition known as septic sore throat and its frequent
companion — scarlet fever — are transmitted through
milk. These conditions are both due to streptococci,
which have been described in an earlier chapter. The
streptococci are conveyed to the cow by a man or woman
who milks a cow while suffering either from a Hght at-
tack of scarlet fever or septic sore throat, or after be-
coming a carrier of the germs. The hands previously in-
fected from the mouth secretions infect the cow's teats.
A little inflammation develops in the lining membrane
of the teats or udder. Since milk is a good food for
streptococci, they multiply greatly in it and so are con-
veyed to those who consume it. There have been out-
breaks of septic sore throat and scarlet fever in which
as many as 2000 people have been infected.

Pasteurization is the only certain protection, but
careful observation of the milkers and thorough daily
inspection of the herd of cows will almost surely pre-
vent infection being passed through the raw milk.

Diphtheria is also passed through milk, but much less
frequently. This generally arises from some ignorant
person who is a diphtheria carrier using a dipper or

USE OF ACQUAINTANCE WITH MICROBES 285

some other utensil to take a sip of milk and then put-
ting the contaminated ladle back again into the milk to
cause infection. The streptococci may contaminate the
milk in the same way. All these bacteria except the
tubercle bacilli actually grow in the milk when they
have once entered it.

The tubercle bacillus has been fought in still other
ways than through safeguarding the milk supply.
Wherever man has been massed, tuberculosis has been
present. Until recently it produced more illness and
deaths than any other infection, and is probably now
only second in its occurrence to pneumonia in the tem-
perate zone and to malaria in the tropical zone. Both
animals and man are almost free of tuberculosis when
living a free hfe in the open air, but when confined in
crowded, closed-in quarters the germ develops freely
in them. In fact, a very great percentage of all persons
dying in civilized communities show evidence of having
at some time been infected with the tubercle bacillus.

For nearly seventy years there has been an almost
continuous decline in the amount of serious tubercu-
losis. Thus in Scotland the death-rate in 1881 was 17
per cent, less than the average death-rate of the ten
years before, of 1891 it was 21 per cent, less, in 1901
it dropped 9 per cent., in 1911 it dropped 21 per cent,
and in 1921 there was a drop of 31 per cent, as com-
pared with the previous ten years.

In the United States in 1901 the death-rate was
195.2 per 100,000, in 1911 it was 164 and in 1920 it
was only 112. During the last fifty years the death-
rate from all causes has been reduced less than one
half, while that from tuberculosis has been reduced
more than two thirds. There is still, however, much

286 WHOS WHO AMONG THE MICROBES

disease and a staggering number of deaths. Thus, in
New York State during 1925, about 10,000 persons
died from tuberculosis. There would have been, how-
ever, more than 40,000 deaths if the amount of tuber-
culosis had remained the same as fifty years ago, the
death-rate having been reduced in New York City from
400 per 100,000 to 100 in that time. This great im-
provement has taken place, as stated in Chapter XIII,
because of the better living conditions, the greater
knowledge of the sources of infection and means of
preventing infection, the removal of many of the sick
to sanatoria, and the tendency of the tubercle bacillus
to decrease in virulence both because it grows more
slowly in the average case and because the most severe
cases are chiefly in hospitals and so the infection
passes usually from the milder cases to new individuals.
Whether or not we obtain a successful vaccine such as
Calmette in his attenuated bacillus hopes to have is
still doubtful. There is no doubt, however, that if we
keep up our attack on the tubercle bacillus in the same
vigorous way that we have been doing, tuberculosis in
the next twenty years will be one of the less important
diseases.

Man's success against the microbes in the tropics is,
on the whole, a striking one. There are important dis-
eases such as pneumonia, typhoid fever, smallpox and
measles which develop in all parts of the world. These
occur in the tropics as elsewhere and we have already
considered them. The essentially tropical diseases are
almost wholly those in which insects or vermin act as
carriers of infection from the sick to the well. The
tropical climate, with its warmth, humidity and luxur-
iant vegetation, makes life easy for the insects and

USE OF ACQUAINTANCE WaTH MICROBES 287

makes it difficult for man to eradicate them. These con-
ditions to some degree pertain in subtropical and tem-
perate regions, where the winter is not cold enough
to destroy semi-tropical vegetation or the dangerous
insects. The infections wliich have occurred in tropical
or subtropical regions are capable of persisting in those
who remove to colder climates. They may occur in other
countries in the season when the conditions approach
those of the tropics. The conditions under which people
live have a great influence in making them more or
less hable to infection.

Most of the tropical diseases due to microbes are
transferred by insects. Yellow fever, once the dreaded
foe of the white man, is transmitted by the mosquito.
The brilliant and heroic investigations of the United
States army commission already described led to an
understanding of the conditions which made it pos-
sible for the mosquito to breed and for the sick man
to infect the mosquito and for the mosquito to infect
man. Once understood, it was simply a challenge to
the human race to exterminate these conditions. Yellow
fever is now endemic only in certain parts of Africa
and in one or two countries of South America. The
human race has practically conquered the yellow fever
microbe and does not need to consider it in planning
trips or places of abode.

Another dreaded disease peculiar to the tropics is
African sleeping sickness. This as already stated is
due to a protozoan called a trypanosome, which is
transmitted chiefly by a biting fly belonging to the
genus Glossina — the tse-tse flj\ This disease is also
largely limited to Africa. The mature flies lay their
eggs in the shade of trees and small shrubs near the

288 WHO S WHO AMONG THE MICROBES

water. These are just where people are apt to pitch
their habitations or make their resting-places and so
make it easy for the sick to infect the flies and for the
healthy to receive infection. The flies generally bite
only in the daytime. It is much more difficult to pre-
vent the spread of sleeping sickness than of yellow
fever. The yellow-fever-carrying mosquito develops in
little pools of water, such as in cisterns, in broken
crockery about the house, etc. It is easy to remove all
such possible places for holding water. The sleeping-
sickness-carrying fly develops in the tropics wherever
shade and moisture exist. Furthermore, there are ani-
mals as well as human beings which can be infected
with the species of trypanosomes which infect man.
Up to the present time only fair progress has been
made. We try to isolate the patients so as to treat them
with curative drugs and to remove them from the
presence of flies. As far as possible we destroy the
animals which act as hosts for the parasites and we
cut down the trees at stopping-places which are found
to shelter the flies. Immigration from and visits to
infected areas are limited as much as possible.

Malaria can properly be considered a tropical dis-
ease, because while it develops also in subtropical and
temperate climates, it is most severe and wide-spread
in the tropics. This disease is carried by a mosquito of a
different species from that carrying the yellow fever
germ. It is called anopheles. These are not home-loving
mosquitos. They develop in the water of swamps,
puddles, shores of stagnant streams. With the rainy
season they increase enormously. When the rainy season
is over, the shallow collections of water dry up as the
larv^ae disappear, while many of the adults keep alive

USE OF ACQUAIXTAXCE WITH MICROBES 289

in shady places and wait for the next rainy season.
Some of these mosquitos breed in tree holes or in the
water contained in bamboo joints.

The outdoor mosquitos only invade human habita-
tions when they are near their breeding-places. Work-
men camping in open ranches or people traveling on
rivers are the most exposed. It is easy to see the diiBcul-
ties which we meet with in trying to ehminate malaria.
In a settled community- it is possible, but in the sparsely
populated regions it is impossible.

We attack the problem in two ways. We use daily
small doses of quinine as a preventive of infection and
larger doses to cure the case; or, if this is impossible,
to ehminate the parasite from the blood and to prevent
infection of mosquitos. Wherever possible we diminish
the number of mosquitos by the drainage or filhng up of
pools or swamps or by cutting down excessive woods.
The homes of the people are built on fairly high and
dry ground. The windows are screened and as far as
possible infected people are isolated. Chronic cases
especially are sought for, and the blood is examined
for the parasite in suspected cases.

We have found an additional means of defense.
Many varieties of fish eat the larvae voraciously. These
are grown in the waters where the mosquitos breed.
By these various means man has made great progress
in the more civilized and well-inhabited regions, but
he sees the time as still far distant when he will obtain
a complete victory over the malarial microbes in all
parts of the world.

Our progress in attacking the microbes causing the
venereal diseases is growing slowly. These ubiquitous
microbes have a peculiar relation to human infections.

290 WHO S WHO AMONG THE MICROBES

Except in very unusual circumstances, there is no ex-
cuse for their transmission. The one who passes the
infection to another is aware of the danger, or at least
should be aware, but the recipient of infection may in
all innocence receive it. In spite of these facts, venereal
diseases still abound and the innocent as well as the
guilty suffer irreparable harm.

The American people have resolved to continue an
ever-increasing battle against the microbes of gonor-
rheal and syphihtic infection. They beHeve that a cour-
ageous facing of facts and the pressing upon the
minds of young men especially the harm that these
infections do, not only to themselves but to innocent
women and unborn children, will persuade them to take
the necessary precautions. The American plan does not
regard venereal disease as a punishment but as a com-
municable disease which must be treated not as a pri-
vate matter but as one of pubhc concern. It emphasizes
the fact that the sex instinct is normal, and urges edu-
cation rather than prohibition. It considers the infected
as patients and not as animals. It urges that society
provide opportunities for healthful recreation. It ex-
pects woman as well as man to take an active part in the
campaign. The progress made is encouraging, consid-
ering the short time that the public has made organized
attacks upon these diseases. The Federal Government
as well as States and cities is appropriating large
sums of money for the prevention of venereal diseases.
Private organizations are giving active and effective
help.

We may conclude our summary by a brief statement
of how vaccines and serums have helped to protect
man from harmful microbes. It is common knowledge

USE OF ACQUAINTANCE WITH MICROBES 291

that many diseases give protection to those who have
recovered from them. No one fears allowing a child
who has just had measles or scarlet fever to be placed
in contact with a child having one of those diseases.
This protection is what we call "specific" — that is, the
child which has recovered from measles is immune to
measles but not to scarlet fever or any other disease.
This immunity is due to two kinds of antibodies and
probably also to other changes not so well recognized.

It was accidentally discovered in the early nineties
that in those that had recovered from several of these
diseases antibodies could be definitely found. These
either neutrahzed the poisons of the germ, as in diph-
theria or tetanus, or together Tv^th certain tissue cells
of the body fought germs and destroj'^ed them, as in the
case of pneumonia. It was discovered that animals in-
jected with these living germs or with their toxins
develop one or the other of these kinds of antibodies,
and that when these injections are repeated from time
to time the potency of the serums gradually increases
until it is so strong that it can be used in human beings,
giving to them somewhat the same protection as if
they had had the disease. It can be used thus either
as a preventive measure or as a curative measure. We
call the microbes themselves or their products vaccines,
because the first vaccine was made from a calf having
cowpox, and now the idea of protection gives the word
its meaning rather than the animal from which it was
derived.

Vaccines may be either the living attenuated virus,
as the cowpox against smallpox, or larger numbers of
the dead germs as in the vaccine against typhoid fever ;
or, instead of living or dead germs, a vaccine may con-

292 WHO S WHO AMONG THE MICROBES

sist of the toxin of the germ. This latter kind can be
used as a preventive in diphtheria, scarlet fever and
tetanus. These toxin vaccines may be used just as de-
veloped in cultures, as in scarlet fever, or the stronger
ones may be changed by the addition of formahn so
that they are less irritating, as in the case of diphtheria
toxoid and tetanus toxoid ; or they may be made into a
mixture "wdth antitoxin — ^the famous toxin-antitoxin
mixture, or the so-called TA. The vaccine causes the
body to produce protective substances in the same way
as does the disease. This is called "active immunity."
It is fairly or quite permanent following the use of some
vaccines and temporary from others.

Horses or other animals producing serums contain-
ing antibodies have themselves been vaccinated, but
when their serum is used to protect human beings or to
cure them the horse serum with its antibodies is simply
transferred and diluted in the human body. This is
called "passive immunity," because the body does not
increase it in any way. The antibody acts essentially
in the body as it would in the fluid of a flask. Unfor-
tunately, passive immunity is not lasting, because the
antibodies are a part of the blood of the horses and
are to some degree ahen to human beings. That is, they
are foreign proteins, and any of them that are left after
neutrahzing or rendering harmless the toxins they
have met are gradually made useless by the cells of
the human body or are ehminated from the system by
the urine. In doing this the human body has rendered
itself sensitive to them as foreign proteins, so that a
second injection is more likely to cause what we call
serum sickness. This is shown usually by a skin re-
action like hives and a temperature. The difference be-

USE OF ACQUAINTANCE WITH MICKOBES 293

tween the more lasting protection afforded by vaccina-
tion as contrasted with the shorter period from the
injection of antibodies is largely due to the fact that
in one case the body develops its own tissue antibodies,
while in the other case it receives the tissue antibodies
of another species.

Man, then, when sick uses an antiserum to help cure
him; when well he uses a vaccine so he may help to
estabhsh an active lasting immunity.

IXDEX

Acid, 24, 47; acetic, 109; in food
medium, 148; indicators for,
47; lactic, 53, 94, 112, 113; re-
action, 26.
Acid- fast bacilli (see tubercle
bacilli, etc.), harmless, 188.

Acid-fast group, 78, 79, 178-88.

Actinomycetes, 79, 219-28; in
lower animals, 221-2; madura
foot and, 227; in man, 223-8;
in meningitis, 225-7; in plants,
221 ; potassium iodide as cure
of, 228; rosettes of, 221-3; in
tonsillitis, 224.

Aerobes, 39, 79.

Agglutination, 19, 61-63; of
pneumococci, 97; of strepto-
cocci, 91, 92-3; in tularemia,
140.

Agglutinins, absorption of, 62-3;
in cholera, 202; in dysentery,
128; in influenza, 145; with
paratj-phoid group, 117; in
pertussis, 149.

Air born microbes, 57, 191, 273.

Alcohol, 53, 231-2, 233.

Alimentary- canal (see intestines,
microbes in)

Alkali, 24; reaction for, 26.

Alkaligenes, 128.

Amoebas, 74, 80, 82, 240-2, 250,
251.

Anaerobes, 39.

Animalcules, 6, 10.

Anthrax, 12, 158; baciUus, 153-5;
bamboo-rod appearance of,
153; hosts of, 153; spores of,
in shaving brushes, 155; vac-
cine, 154.

Antibodies, 11, 48, 58, 59, 60, 65,
86, 95-6, 100, 292-3.

Antigens, 65.

295

Antiseptics, 15.

Antitoxin, 45, 58, 94, 100, 159-60,

161, 163, 170-3, 174, 175, 292.
Arnold sterilizer, 27.
Arsenic, 214.
Arsphenamine, 214.
Arthritis, 242.
Ascus, 81.
Aspergillus, 234.
Autoclave, 27.

Babesia bigemina, 246.

BaciUi, acid-fast, 23, 178-88;
anaerobic, 77, 156-63; aerobic,
77; diphtheria, 23, 167-77;
drumstick, 157; encapsulated,
76; gas gangrene, 162; influ-
enza, 76, 141-6; paratvphoid A,
B, 116, 117; tubercle', 23, 178-
86; wound, 77, 156-63.

Bacillus, 152; anthracis, 77, 153-5
(see anthrax bacillus) ; botu-
linus, 77, 115, 160-1; coli, 115;
dysenteriae, 127; influenzae, 76,
147-9; of lockjaw (see teta-
nus); "long life," 110, 113;
megetarium, 153; pertussis, 76,
147-9; pestis, 76, 133-5; pro-
digiosus, 75; pyocyaneus, 76;
subtUis, 152; tetani, 77, 157-60;
tuberculosis, 79, 178-86; tvphi,
120-7; welchii, 162.

Bacteria, 28, 29, 74, 76; division
of, 31-3; description of, 29;
estimation of, lIO-l; families
of, 70; food-poisoning, 77, 115-
20; in food and drink. 111; at
birth. 111; growth of, 31-3
higher, 33; life-giving, 101
measurement of, 31 ; motion of,
30-1 ; nitrogen - fixing, 101
number of, in intestines, 110

296

INDEX

port of entry of, 111 ; shape of,
33-4; size of, 31; in soil, 77;
structure of, 29; and suppura-
tion, 15; vegetative, 30.

Bacteriophage, 48-50.

Bacterium tularense, 138; car-
riers of, 138; protection from,
140.

Balance between man and mi-
crobe, 65.

Black death, 132.

Blights, 53, 75.

Blood-loving bacilli, 141-9.

Bordet-Gengou bacillus, 147-9 ;
food medium, 147-8.

Borrelia, classification of, 210; in
lower animals, 211; species of,
211.

Botulinus bacillus, 160-1; toxin
of, 161 ; protection against,
161 ; antitoxin against, 161.

Broth, nutrient, 27.

Brucella, 128, 129.

Bubonic plague, 134.

Bulgarians, long-lived, 113.

Canned foods and spores, 151.

Canning, 9, 53.

Carbohydrates, 46, 47.

Carriers of germs, 43, 56, 57, 66,
67, 274, 275; insect, 66, 138,
286-7; of plague, 135-6; of ty-
phoid, 120-7.

Cells, white-blood, 63; as phago-
cytes, 64; defensive power of,
64.

Cheese, molds and, 233; strep-
tococci and, 94; yeasts and,
233.

Cholera, 4, 50, 55, 190-203; in
Asia, 198; Broad Street pump
epidemic, 191-4; Dunham and,
200-1; in Russia, 198; symp-
toms, 196; vibrio, 129, 194-203;
accidental infection, 195-6;
conveyed by water, 190-4; ex-
periments on humans, 196-7;
killed by acid, 195; serologic
tests of, 202; vaccine of, 203.

Chlorine, water disinfectant,
278-9.

Ciliates, 74, 82.

Classes of microbes, 28-9, 70.

Classification, 9, 28, 74.

Cleanliness and health, 274-5.

Clostridium, 152, 156-63; botuli-
num, 161; chaurei, 162; vaccine
of, 162.

Club-shaped group, 164-77.

Cocci, 33; pyogenic, 84.

Coccidium, 251.

Coccus familv, 74, 84-100.

Coiled hair family, 74, 77, 204-
18.

"Cold," 86; common, 269.

Colony, fishing, 20; types, 20; va-
riations, 45, 116.

Comma family, 74, 77, 190-203;
bacillus, 194-203.

Communal life, 54.

Comparator block, 24, 26.

Complement, 60.

Corynebacterium diphtheriae, 164-
77; pseudo diphtherium, 168-9;
flavidum, 169; xerosis, 169.

Cowpox vaccine, 10, 11.

Culture, media, 15, 23 (see me-
dium); pure, 9, 14, 19, 20, 35;
methods for obtaining, 19, 20,
72; colonies, 19, 20.

Dengue or break-bone fever, 260-
1 ; and mosquitoes, 261.

Dick test 93.

Diphtheria, 23, 78, 164-77, 292;
antitoxin, 170-3; conquest of,
177; history, 167; and strepto-
cocci, 89; vaccine, 58, 59, 292;
wiped out, 176; bacilli, 44, 56,
58, 164-77; carriers, 166; cul-
tures, 167-8; and milk, 284-5;
non-virulent, 168; pseudo, 168-
9; toxin, 44-5, 58, 165-6.

Disease, communicable, 16, 275;
conquest of, 13; contagious,
43; foot-and-mouth, 256-7; and
germs, 10; infectious, 10, 12,
16, 65; mosaic, 258; in tropics,
286-9; venereal, 99; virus, 252-
71 ; and witchcraft, 4.

Disinfection, 16.

Distemper, 129.

Droplet infection, 56, 57-8.

INDEX

297

Drying, effect of, on microbes,

41, 42, 52.
Dysentery, phage in, 50; specific

bacterial, 127; bacillus, 127;

amebic, 240-2; cause of, 240-1;

prevention, 241 ; cure, 242.

Eberthella typhi, dvsenterias,

127.
Electricity and microbes, 40.
Emetin, 242.
Encephalitis, lethargica, 247;

epidemic, 270-1.
Endotoxin, 48.
Ensilage, 53.
Epidemics, 4, 54, 67, 68, 87, 99,

132-3, 137, 141, 143-5, 152, 190,

198-200, 235, 258, 274.
Escherichia coli, 115.
Estivo-autumnal malaria, 242-3.
Enzymes, 46, 49.
Erysipelas, 88, 89.
Exotoxin, 45-6, 48, 59, 85, 98.

False-branching family, 74, 78.

Family, branching, 74, 219-28;
coccus, 74, 84-100; coiled hair,
74, 204-18; comma, 74, 190-203;
groups, 69, 74; non-spore-bear-
ing, 74, 80; nitrogen-using, 74,

80, 101-9; relationships, 69-83;
resistant, 150-63; spore-bear-
ing, 74, 150-63; "Tree," 69, 80,

81, 83.

Favus, 34, 230, 235.

Fermentation, 9, 46-7.

Filters, ultramicroscopic, 253-5.

Filtration of water, 278.

Fishing for microbes, 20 (see
also frontispiece).

Flagella, 30.

Flagellates, 74, 80, 82, 240, 247,
250.

Fleas, 66; and plague, 135-6.

Flies, carriers of disease germs,
66, 275; in kala-azar, 250; in
sleeping sickness, 248, 287-8;
in tularemia, 138, 139; and ty-
phoid, 43; tsetse, 287-8; sand,
250.

Food (see media), bacteria in,
115-20; handlers, 66; regula-

tions for, 126; poisoning, 53,

115-20.
Foot-and-mouth disease, 256-8.
Freezing, effects of, on microbes,

38, 53.
Fumigation, 57-8.
Fungi, 74, 229-38; imperfecti, 74,

81.

Gas, demonstration of, 47.

Gas gangrene bacilli, 162.

Generation, spontaneous, 7-9, 150.

Glanders, 188-9; disappearing,
188-9; mallein, 189; bacillus,
188-9.

Glassware, preparation of, 23-5.

Gonococcus, 98-9; cause of ar-
thritis, 98; of blindness, 98; of
venereal disease, 99.

Gram stain, 18, 21.

Ground squirrels and plague,
135-6.

Hands, carriers of infection, 56.

Hanging drop for studying mi-
crobes, 19, 21.

Heat-loving microbes, 38.

Hemolysis, 85, 91.

Hemophylus influenzae, 141-6;
lacunatus, 146; pertussis, 147-9,

Higher bacteria (see Actinomy-
cetes).

Hosts of germs among lower ani-
mals, 35, 37, 42, 43-4, 135-7,
140, 239, 246, 249, 251 (see also
carriers).

Hydrophobia (see rabies).

Ice, effects of, on germs, 38,
Immunity, acquired, 51, 57; ac-
tive, 292; in babies, 177; to
black leg, 162; cellular, 63; to
cholera, 203; to diphtheria, 59,
170-7; to infantile paralysis,
263; to measles, 265; to men-
ingitis, 99; to microbes, 51, 57,
60, 64, 65, 291-3; mother's, 177;
natural, 51, 57; passive, 292; to
pertussis, 149; to smallpox, 10,
11; to tetanus, 157, 160; to
tuberculosis, 183, 184, 185-6; to
typhoid, 281.

298

INDEX

Incubator, living, 124; natural,

111; special, 38.
Indian-club-shaped group, 78.
Indicators, for acids, 147.
Infantile paralysis, 88-9 (see

poliomyelitis).
Infection, through air, 191, 273;

through carrier, 43, 57, 66, 67,

120-7, 274, 275 ; by contact, 56 ;

droplet, 56.
Influenza, 55, 141-6; epidemic,

143-6; meningitis, 146; bacilli,

141-6; near relative of, 146.
Infusoria, 74.
Insect-borne infection, 66, 138,

139, 275, 286-7.
Intestines, microbes in, 110-30;

lactic acid bacilli in, 112-3.
Intestinal flora, control of, 112-3,

129-30.
Invaders, secondary, 89.

Kala-azar, 249.
Koch-Week's bacillus, 146.

Lactic-acid bacilli, 112-14.

Lactobacillus acidophilus, 113-4;
implantation of, 114; bulgari-
cus, 113.

Leak of nature, 102.

Legumes and nitrogen-fixing bac-
teria, 102-4.

Leishman-Donovan bodies, 249-
50; culture of, 250; fly in, 250.

Leishmania donovani, 250; trop-
ica, 250; transmission and
treatment of, 250.

Leprosy, 187-8; cases in U. S.,
187; not highly contagious,
187; unclean disease, 178, 187;
bacilli, 187-8.

Leptospira, in infectious jaun-
dice, 217; interrogans, in yel-
low fever, not its cause, 216-8.

Leucocytes and immunity, 63.

Lice in typhus, 269-70.

Life cycle, 43, 46, 53, 55, 101,
102, 106-8, 244.

Light, efi'ect of, on microbes, 39-
40, 42.

Litmus, 47.

Lockjaw bacillus (see tetanus
baciUus).

"Long life" bacillus, 110, 113.
Lumpy jaw, 219, 222.

Malaria, 4, 35, 55, 82, 242-4;
cause, 242; life cycle of germ
of, 244; misnomer, 239, 242;
mosquitoes in, 245, 288-9;
quinine in, 243; types of,
242-3.

Malta fever, 128.

Measles, 67, 265-8, 291; con-
valescent serum in, 267-8;
streptococcus, 88, 89; year,
265-6.

Medium, culture, 15, 23; agar-
agar, 15, 28; blood, 143; beef
heart, 26; Bordet-Gengou, 147-
8; chocolate, 143; complex,
essentials of, 36; differential,
27; gelatine, 15, 27-8; infusion,
26; nutrient, 27, 28; oleate-
blood-agar, 143; peptone, 26;
reaction of, 26; soaps in, 143;
solid, 27; sterilization of, 27.

Meningitis, 100; due to actino-
mycetes, 225-7; due to yeasts,
237-8.

Meningococcus, 99-100 ; anti-
bodies, 100; carriers, 99; im-
munity to, 99; tests for, 100;
treatment of infections of, 99-
100.

Mercury, in syphilis, 214, 216.

Microbes, animals free from, 112;
antagonisms of, 42; balance of,
114; behavior of, 36-50; and
civilization, 13; control of,
272; division of, 19; drying of,
112; electric charge and, 40;
on food, 111; gram-ampho-
phile, negative, positive, 22;
growth of, 19; in intestines,
110-30; harmful, helpful, 112;
magnification of, 17; motion
of, 19; at poles, 36; pressure
on, 40-1; radium on, 40; sun
on, 39, 40; shape, 19; size, 19;
specificity of, 16, 46; study of,
in hanging drop, 18-19; ultra-
microscopic, 6, 252; unknown,
252-71 (see virus) ; variability
of, 46, 72.

INDEX

299

Microscope, 6, 17, 18; dark field,
18; use of, 30-1.

Milk, 51-2, 117, 127] clean, 272;
diphtheria and, 285-6; food for
germs, 51-2, 274; frigeration
of, 53; pasteurization of, 52,
277-8, 284; products of, 53;
sour, 52, 114, 272; and strep-
tococci, 284; and typhoid, 127,
276; and summer diarrhoea of
infants, 281-3; and tubercu-
losis, 283-4.

Molds, 28, 33, 34, 35, 74, 79, 80,
81 ; yeasts and, 229, 238 ; char-
acteristics of, 229-30; imper-
fect, 74, 81; and sugar, 230;
nonseptate, 74, 81 ; septate, 74,
81; where found, 229-30; in
cheese, 233; in favus, 230, 235;
useful, 233; in fermentation,
233-4; gallic acid produced by,
234; harmful, 234-6; epidemics
from, 235.

Morax-Axenfeld bacilli, 146.

Mosaic disease, 258-9.

Mosquitoes, carrying malarial
germs, 243-5, 273; character-
i istics of, 245; in yellow fever,

260, 287.

Motility of bacteria, 30.

Mumps, 269.

Mycelium, 80.

Mycobacterium, 178-88; leprae,
187-8; tuberculosis, 178-87.

Mycomycetes, 81.

Nature of microbes, 51.

Nature's methods, control of, 55.

Neisseria gonorrhoea, 98-9 ; in-
tracellularis, 99-100.

Nitrogen cycle, 106-7,

Nitrogen-fixing bacteria, 101,
102-4.

Nitrogen-using-family, 74, 75,
80, 101-9.

Nocardia, 220.

Nodules on legumes, due to bac-
teria, 102-4.

Nomads, 54.

Opsonins, 64.
Osmosis, 40-1.

Oxidizers, of alcohol to acetic
acid, 109; of ammonia to ni-
trite, 104-5; bacteria, 101, 104-
6, 109; of nitrites to nitrates,
104-5.

Oxygen, and microbes, 37, 39.

Ovsters and U^phoid fever, 127,
279-80.

Parasite, 28, 37, 42, 239.

Paradysentery bacilli, 128.

Paratyphoid bacilli, 117,

Pasteur's tribe, 131-7.

Pasteurella avicida, 131 ; vaccine
of, 131; pestis, 133-5.

Pasteurization of milk, 38, 39,
53, 277-8, 284.

Peptone solution, Dunham's, 201.

Pernicious malaria, 55, 242-3.

Pertussis, bacillus, 147-9; vac-
cine, 149.

Petri dish, 19.

Pfeiifer's phenomenon, 203.

Pfeifferella mallei, 188-9 (see
glanders bacillus).

Phenolphthalein, 47.

Pickling, or corning, 41.

Plague, bubonic ("black death"),
4, 55, 132-7; accidental, 134;
prevention, 5, 137; year, 5,
132; bacilli, 132-5; carriers of,
135-6; fleas and, 135-6; rats
and, 135-6; vaccine of, 137.

Pneumonia, 94, 95.

Pneumococcus, 94-6; antibodies
against, 95; determining types
of, 97; identification of, 96;
potency of, 95-6; types, 95.

Poliomyelitis, 264-5 ; epidemic,
264; lameness in, 264, 165; sus-
ceptibility to, 265; treatment
of, by human serum, 265.

Potassium iodide in syphilis, 215;
in actinomyces, 228; in yeast
infection, 238; in sporothrix
infection, 238.

Pressure, effect of on microbes,
40-1.

Prevention of amebic dysentery,
241; anthrax, 154-5; cholera,
203; diphtheria, 170-5, 177;
disease, 16, 65-8, 275, 276; food

300

INDEX

poisoning, 120, 161 ; malaria,
243, 288-9; measles, 267-8;
plague, 137; rabies, 261, 262,
264; smallpox, 11, 268; sleeping
sickness, 287-8; summer diar-
rhoea, 281-3; syphilis, 213-14,
289-90; tetanus, 159-60; tick
fever, 246; tuberculosis, 185-6;
venereal diseases, 89-90; whoop-
ing cough, 137; yellow fever,
260, 287 (see also immunity
and vaccine).

Proof that a microbe causes spe-
cific disease, 12.

Protista, 14, 28.

Protozoa, 28, 34, 35, 43, 77, 80,
82, 239-51; carriers, 251; diar-
rhoea, 251 ; endemic, 239 ; help-
ful and harmful, 239-40; in in-
testines, 250-1 ; pure culture of,
207; in soil, 240; transmission
of, 239.

Ptomaine poisoning, 160.

Puerperal fever, 15, 16, 89, 91.

Pyorrhcea, 242.

Quinine, in malaria, 243.

Rabbit disease, 131 (see tula-
remia).

Rabies, 11, 261-4; cats and, 264;
dogs and, 44, 261 ; negri bodies
in diagnosis of, 263; preven-
tion of, 261; susceptibility to,
261-2; symptoms of, 263; vac-
cine aga'inst, 12, 262-3, 264.

Rat, infection through, 120; in
plague, 135-6.

Refrigeration and microbes, 53.

Relapsing fever, 209-10.

Relationships of microbes, 69-84.

Resistance to actinomyces, 223-4;
to staphylococcus, 86; to tuber-
culosis, 183 (see also immunity,
etc.).

Retting of flax, 53.

Rickettsia, 269.

Salmonella enteritidis, 118; sui-

pestifer, 118.
Saprophytes, 37.
Scarlet fever, 89-94, 291; cause

of, 89-94; horse response to,

92; and streptococci, 89-94;
toxin of, 93-4; milk and, 284;
Dicks and, 93.

Schick Test, 58, 91, 93, 94, 175-6;
reliability, 176.

Septicemia, streptococcus, 88, 94.

Septic sore throat and milk, 284.

Shellfish and typhoid fever, 279-
80.

Serums, 65, 290-3; antimicrobal,
60; bacteriolytic, 60; germi-
cidal, 60; of animals immu-
nizer against cholera, 203.

Sewage and civilization, 54.

Sexual phases, of yeasts and
molds, S4; of protozoa, 35; of
malarial germs, 244.

Shaving brushes and anthrax
spores, 155.

Shellfish, 279-80.

Size of bacteria, 31-2.

Sleeping sickness, tropical, 247-9
(see trypanosomiasis).

Smallpox, 4, 10-11, 268-9; control
of, 11; Copman on, 5; and
cowpox, 10, 11, 268; and Jen-
ner, 10-11; Macauley on, 5;
virus, and immunity, 10; and
Lady Montague, 10; vaccine,
268, 269; bovine, 269,

Soap, medium, 143.

Sodium hydroxide, 47; sulphite,
47.

Soil, chemists of, 101 ; depletion,
53; microbes, 101; study of,
108.

Sour milk, 52, 114.

Spirilla, 33, 77, 80.

Spirillum rubrum, 77; cholerae,
see cholera vibrio, 194-203.

Spirochete, "pale," 204; of re-
lapsing fever, 209.

Spirochete, 33, 77, 80, 204-18.

Spontaneous generation, 7-9, 150.

Spores, 9, 14, 25, 29, 30, 150.

Spore-bearing family, 74, 80, 150,
63; bacilli, 115, 150-63; infec-
tion from, 152.

Spore bearers in soil, 150-63,

Sporothrix infection, 238.

Sporozoa, 74, 80-2, 251.

Stains, 14, 18, 19, 21-23.

IXDEX

301

Stain, Gram's, 18, 21; alkaline-
methylene blue, 32; special, 23.

Staphylococcus, 50, 86-7; albus,
86; aureus, 86; citreus, 86.

Sterilization, 15, 23; of glass-
ware, 23, -25, 26; of media, 27.

Sterilizers, Arnold, 26, 27; auto-
clave, 23, 27; dry heat, 25.

Streptococcus, 70, 84-94; aggluti-
nation of, 92-3; anhemolytic,
91; cause of scarlet fever, 89-
94; in cheese, 94; in erysipelas,
88; green, 91, 94; groups, 91;
in heart disease, 94; hemolysis
by, 85; hemolytic, 91; lactic
acid producer, 94; in IjTnphan-
gitis, 88; pyogenes, 70, Si; in
rheumatism, 94; septicemis, 86;
wronarfully accused, 89; toxin,
92, 93-4.

Sugar, 41, 47; and fruit preserv-
ing, 41; and yeasts, 230; solu-
tions, 47; and alcohol, 230; and
molds, 230.

Susceptibility, 42, 48; anthrax,
154; botulinus, 161; to diph-
< theria, 58; to food poisoning

bacteria, 120; to measles, 266;
pneumonia, 25 ; to staphylo-
cocci, 86-7; to streptococcus, 88,

S\Tnbiosis, 41-2.

Syphilis, 4, 60, 99, 204, 205, 207;
control of, 216; immoral dis-
ease, 212; origin of name, 212;
prevention of, 213-4; treatment
of, 213-4, 215.

Tanning of leather, 53.

Temperature relations of mi-
crobes, 37-39, 53; optimums, 38.

Tetanus, 157-60; antitoxin, 59-
60; in child-birth, 158; cure of,
160; prevention of, 160; bacilli,
carriers of, 157; and wounds,
158.

Texas fever, cause, prevention,
transmission of, 246.

Ticks, 66; in rickettsia, 269; in
Texas fever, 246-7; in tula-
remia, 139; in typhus fever,
269-70.

Toxin, botulinus, 116, 161; diph-
theria, 44-6, 58, 165-6; endo-
toxin, 48, 59, 85, 92; exotoxin,
45-6, 48, 58, 59, 85, 98; scarlet
fever, 92, 93-4; tetanus, 158-9.

Tree of evolution of microbes,
hypothetic, 80-1, 83.

Treponema, pallidum, 204-8, 212-
15; cause of syphilis, 204-7;
classification of, 207-8; culti-
vation of, 207; activities of,
212; cuniculi, 216; pertenue,
215-6.

Trj-panosome, 247-9, 287; pure
cultures of, 248; in sleeping
sickness, 248-9, 287.

Trypanosomiasis, cure of, 245,
287; sjTnptoms of, 249.

Tsetse flv, 287-8.

Tubercle bacillus, 178-81, 183-6;
baby feeding of, 185-6; culti-
vation of, 179-80; staining of,
179; tuberculosis from, 184-5;
tvpes of, 180-2; vaccine (Cal-
mette's), 185-6.

Tuberculosis, 4, 178-82, 285; ar-
rested, 182-3; in cattle, 180-1,
183-4, 185; communicable, 179;
decline of, 285-6; experimental,
178-81; and milk, 283-4, 285;
and Trudeau, 182-3.

Tularemia, 138-40.

Typhoid, bacillus, 120-7; aggluti-
nation of, 61-2; carriers, 120-7;
fly, 43; "Mary," 121-6; milk
and, 276; safeguards against,
121, 276-80; shellfish and, 279-
80; water and, 278.

Typhus fever, 269-70.

Ultramicroscopic microbes, 6, 49,
71, 252-71.

Vaccine, 16, 65, 67, 290-3; an-
thrax, 154-5; bacteria, 7; the
first, 131; Calmette's, 185-6;
cholera, 203; diphtheria, 58,
174-7, 292; plague, 137; small-
pox, 10, 11, 65, 268, 269; whoop-
ing cough, 149.

Venereal diseases, 99, 289-90.

302

INDEX

Vibrio, 33, 37; comma (see chol-
era vibrio) harmless, 201-2.

Vibrion, septique, 156, 162; bu-
terique, 156.

Vincent's angina, 169.

Vinegar, 109.

Virus diseases, similarity of,
256.

Viruses, filterable, 118, 252-71.

War, World, 92, 137, 155, 159-60;
wounds, 158.

Wassermann Test, 60-1, 214.

Water, chlorination of, 278-9;
cholera and, 190-5; clean, 272,
276; filtration of, 278; and ty-
phoid, 127, 278.

Whooping cough, 147; bacillus,
147-9; vaccine, 149.

Widal Test, 61-2.

Witchcraft, 4.

Wines and beers, 53; sick, 53;
gods of, 272.

Wool sorter's disease, 155.

Wound bacilli, 77, 156-63; anti-
toxin against, 162.

Yaws, 216.

Yeasts, 28, 34, 35, 53, 74, 79, 80,
81; and alcohol, 231-2; in
brains of humans, 236-8; in
bread, 53, 233; characteristics
of, 34-5, 229-30; in cheese rip-
ening, 233; and glycerine, 233;
harmful, 234, 236-8; in intesti-
nal putrefaction, 233; and
molds, 34-5, 229-38; potassium
iodide in infections with, 238;
useful, 231-3; vitamins of, 232;
where found, 229-30; in wines
and beers, 53, 231-2.

Yellow fever, 4, 54, 216, 259-
60, 287; control of, 259, 260,
287; filterable virus, cause of,
218, 259; investigations of,
259-60, 287; spirochetes in,
216-8; and mosquitoes, 260,
287, 288.

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